Uninstalling previous during update installation hangs?

I was installing version 3.16.3 30-04-2016 on Ubuntu 12.04 LTS (Kernel 3.13.0-86-generic #130~precise1-Ubuntu SMP Tue Apr 19 19:25:46 UTC 2016) that runs on my Sony VAIO laptop and the script seemed hung at the uninstall previous step. However, I discovered by allowing it to sit overnight, that it did end eventually. This seems to me to be a bug. I have never before encountered software whose uninstallation takes so long, and I have been around a while. I also observed this when I previously installed 3.16.2, but thought perhaps it was a glitch that would not repeat for 3.16.3.

Did not run hp-doctor at the time the bug was observed because I didn't know about it. HP 8600 Printer works OK. 7590 is kept as hot plug replacement in the event 8600 goes down. Output from hp-check follows:

Saving output in log file: /home/norisezp/hp-check.log

HP Linux Imaging and Printing System (ver. 3.16.3)
Dependency/Version Check Utility ver. 15.1

Copyright (c) 2001-15 HP Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Note: hp-check can be run in three modes:
1. Compile-time check mode (-c or --compile): Use this mode before compiling the
HPLIP supplied tarball (.tar.gz or .run) to determine if the proper dependencies
are installed to successfully compile HPLIP.
2. Run-time check mode (-r or --run): Use this mode to determine if a distro
supplied package (.deb, .rpm, etc) or an already built HPLIP supplied tarball
has the proper dependencies installed to successfully run.
3. Both compile- and run-time check mode (-b or --both) (Default): This mode
will check both of the above cases (both compile- and run-time dependencies).

Check types:
a. EXTERNALDEP - External Dependencies
b. GENERALDEP - General Dependencies (required both at compile and run time)
c. COMPILEDEP - Compile time Dependencies
d. [All are run-time checks]
PYEXT SCANCONF QUEUES PERMISSION

Status Types:
    OK
    MISSING - Missing Dependency or Permission or Plug-in
    INCOMPAT - Incompatible dependency-version or Plugin-version

---------------
| SYSTEM INFO |
---------------

 Kernel: 3.13.0-86-generic #130~precise1-Ubuntu SMP Tue Apr 19 19:25:46 UTC 2016 GNU/Linux
 Host: PHILS-Linux
 Proc: 3.13.0-86-generic #130~precise1-Ubuntu SMP Tue Apr 19 19:25:46 UTC 2016 GNU/Linux
 Distribution: ubuntu 12.04
 Bitness: 32 bit

-----------------------
| HPLIP CONFIGURATION |
-----------------------

HPLIP-Version: HPLIP 3.16.3
HPLIP-Home: /usr/share/hplip
HPLIP-Installation: Auto installation is supported for ubuntu distro 12.04 version

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.16.3

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.16.3
html=/usr/share/doc/hplip-3.16.3
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp
bin=/usr/bin
apparmor=/etc/apparmor.d
# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.16.3
restricted-build=no
ui-toolkit=qt4
qt3=no
qt4=yes
policy-kit=no
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no
apparmor_build=no

Current contents of '/var/lib/hp/hplip.state' file:
Plugins are not installed. Could not access file: No such file or directory

Current contents of '~/.hplip/hplip.conf' file:
[upgrade]
notify_upgrade = true
last_upgraded_time = 1462027207
pending_upgrade_time = 0
latest_available_version = 3.16.3

[last_used]
device_uri = "hp:/net/Officejet_Pro_8600?ip=10.0.0.252"
printer_name =
working_dir = .

[settings]
systray_visible = 0
systray_messages = 0

[commands]
scan = /usr/bin/xsane -V %SANE_URI%

[refresh]
rate = 30
enable = false
type = 1

[polling]
enable = false
interval = 5
device_list =

[fax]
voice_phone =
email_address =

[installation]
date_time = 04/30/2016 16:05:29
version = 3.16.3

 <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>

--------------------------
| External Dependencies |
--------------------------

 gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.05 OK -
 scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.22 OK -
 xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.998 OK -
 cups CUPS - Common Unix Printing System REQUIRED 1.1 1.5.3 OK 'CUPS Scheduler is running'
 policykit PolicyKit - Administrative policy framework OPTIONAL - 0.104 OK -
 network network -wget OPTIONAL - 1.13.4 OK -
 avahi-utils avahi-utils OPTIONAL - 0.6.30 OK -
 dbus DBus - Message bus system REQUIRED - 1.4.18 OK -

-------------------------
| General Dependencies |
-------------------------

 libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.0.1 OK -
 python-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.0.0 OK -
 reportlab Reportlab - PDF library for Python OPTIONAL 2.0 2.5 OK -
 python-notify Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
 pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 4.9.1 OK -
 python-xml Python XML libraries REQUIRED - 2.0.1 OK -
 libusb libusb - USB library REQUIRED - 1.0 OK -
 cups-image CUPS image - CUPS image development files REQUIRED - 1.5.3 OK -
 libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.4.3 OK -
 sane-devel SANE - Scanning library development files REQUIRED - 1.0.22 OK -
 pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 1.1.7 OK -
 python2X Python 2.2 or greater - Python programming language REQUIRED 2.2 2.7.3 OK -
 pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 REQUIRED 4.0 4.9.1 OK -
 libjpeg libjpeg - JPEG library REQUIRED - - OK -
 libpthread libpthread - POSIX threads library REQUIRED - 2.15 OK -
 python-devel Python devel - Python development files REQUIRED 2.2 2.7.3 OK -
 cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - 1.5.3 OK -
 sane SANE - Scanning library REQUIRED - 1.0.22 OK -

---------------
| COMPILEDEP |
---------------

 libtool libtool - Library building support services REQUIRED - 2.4.2 OK -
 gcc gcc - GNU Project C and C++ Compiler REQUIRED - 4.6.3 OK -
 make make - GNU make utility to maintain groups of programs REQUIRED 3.0 3.81 OK -

----------------------
| Python Extentions |
----------------------

 cupsext CUPS-Extension REQUIRED - 3.16.3 OK -
 hpmudext IO-Extension REQUIRED - 3.16.3 OK -

-----------------------
| Scan Configuration |
-----------------------

 scanext Scan-SANE-Extension REQUIRED - 3.16.3 OK -
 hpaio HPLIP-SANE-Backend REQUIRED - 3.16.3 OK 'hpaio found in /etc/sane.d/dll.conf'

-----------------------
| Other Dependencies |
-----------------------

------------------------------
| DISCOVERED SCANNER DEVICES |
------------------------------

device `hpaio:/net/Officejet_Pro_8600?ip=10.0.0.252' is a Hewlett-Packard Officejet_Pro_8600 all-in-one
device `hpaio:/net/Officejet_Pro_L7500?ip=10.0.0.253' is a Hewlett-Packard Officejet_Pro_L7500 all-in-one

--------------------------
| DISCOVERED USB DEVICES |
--------------------------

No devices found.

---------------------------------
| INSTALLED CUPS PRINTER QUEUES |
---------------------------------

Officejet_Pro_8600
------------------
Type: Printer
Device URI: hp:/net/Officejet_Pro_8600?ip=10.0.0.252
PPD: /etc/cups/ppd/Officejet_Pro_8600.ppd
PPD Description: HP Officejet Pro 8600, hpcups 3.12.2
Printer status: printer Officejet_Pro_8600 is idle. enabled since Thu 11 Feb 2016 09:52:49 AM MST
Communication status: Good

Officejet_Pro_8600_fax
----------------------
Type: Fax
Device URI: hpfax:/net/Officejet_Pro_8600?ip=10.0.0.252
PPD: /etc/cups/ppd/Officejet_Pro_8600_fax.ppd
PPD Description: HP Fax4 hpcups
Printer status: printer Officejet_Pro_8600_fax is idle. enabled since Thu 11 Feb 2016 09:53:06 AM MST
Communication status: Good

Officejet_Pro_L7500
-------------------
Type: Printer
Device URI: hp:/net/Officejet_Pro_L7500?ip=10.0.0.253
PPD: /etc/cups/ppd/Officejet_Pro_L7500.ppd
PPD Description: HP Officejet Pro l7500, hpcups 3.12.2
Printer status: printer Officejet_Pro_L7500 disabled since Thu 30 Jul 2015 01:53:36 PM MFile "/usr/lib/cups/filter/hpcups" not available: No such file or directory
error: Unable to communicate with device (code=12): hp:/net/Officejet_Pro_L7500?ip=10.0.0.253
error: unable to open channel
error: Communication status: Failed

Officejet_Pro_L7500_fax
-----------------------
Type: Fax
Device URI: hpfax:/net/Officejet_Pro_L7500?ip=10.0.0.253
PPD: /etc/cups/ppd/Officejet_Pro_L7500_fax.ppd
PPD Description: HP Fax hpcups
Printer status: printer Officejet_Pro_L7500_fax disabled since Thu 30 Jul 2015 01:53:39 File "/usr/lib/cups/filter/hpcupsfax" not available: No such file or directory
error: Unable to communicate with device (code=12): hpfax:/net/Officejet_Pro_L7500?ip=10.0.0.253
error: unable to open channel
error: Communication status: Failed

--------------
| PERMISSION |
--------------

-----------
| SUMMARY |
-----------

Missing Required Dependencies
-----------------------------
None

Missing Optional Dependencies
-----------------------------
None

Total Errors: 2
Total Warnings: 0

Done.