3.12.11-1 (debian experimental) fixes the problem for me

$ hp-scan -g

HP Linux Imaging and Printing System (ver. 3.12.11)
Scan Utility ver. 2.2

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hp-scan[7586]: debug: hp:/net/Officejet_Pro_L7500?zc=Printer: back_end:hp is_hp:True bus:net model:Officejet_Pro_L7500 serial: dev_file: host:Printer zc:Printer port:1
hp-scan[7586]: debug: Cache miss: officejet_pro_l7500
hp-scan[7586]: debug: Reading file: /usr/share/hplip/data/models/models.dat
hp-scan[7586]: debug: Searching for section [officejet_pro_l7500] in file /usr/share/hplip/data/models/models.dat
hp-scan[7586]: debug: Found section [officejet_pro_l7500] in file /usr/share/hplip/data/models/models.dat
hp-scan[7586]: debug: hpfax:/net/Officejet_Pro_L7500?zc=Printer: back_end:hpfax is_hp:True bus:net model:Officejet_Pro_L7500 serial: dev_file: host:Printer zc:Printer port:1
hp-scan[7586]: debug: hp:/net/Officejet_Pro_L7500?zc=Printer: back_end:hp is_hp:True bus:net model:Officejet_Pro_L7500 serial: dev_file: host:Printer zc:Printer port:1
hp-scan[7586]: debug: hp:/net/Officejet_Pro_L7500?zc=Printer: back_end:hp is_hp:True bus:net model:Officejet_Pro_L7500 serial: dev_file: host:Printer zc:Printer port:1
hp-scan[7586]: debug: hp:/net/Officejet_Pro_L7500?zc=Printer: back_end:hp is_hp:True bus:net model:Officejet_Pro_L7500 serial: dev_file: host:Printer zc:Printer port:1
hp-scan[7586]: debug: Device URI socket://192.168.1.5:9100 is invalid/unknown
hp-scan[7586]: debug: Exception: 4 (Unknown/invalid device-uri field)
hp-scan[7586]: debug: Device URI socket://192.168.1.5:9101 is invalid/unknown
hp-scan[7586]: debug: Exception: 4 (Unknown/invalid device-uri field)
hp-scan[7586]: debug: Device URI dnssd://NM1662E6._ipp._tcp.local/ is invalid/unknown
hp-scan[7586]: debug: Exception: 4 (Unknown/invalid device-uri field)
hp-scan[7586]: debug: Device URI cups-pdf:/ is invalid/unknown
hp-scan[7586]: debug: Exception: 4 (Unknown/invalid device-uri field)
hp-scan[7586]: debug: {'hpaio:/net/Officejet_Pro_L7500?zc=Printer': ['Officejet_Pro_L7500', 'Officejet_Pro_L7500_old_driver', 'Officejet_Pro_L7500_pour_scan', 'OJ_Pro_L7500_2pagesA4'], 'hpaio:/net/Officejet_Pro_8600?zc=HP8F7B78': ['Officejet_Pro_8600']}

-----------------
| SELECT DEVICE |
-----------------

  Num       Scan device URI                          
  --------  -----------------------------------------
  0         hpaio:/net/Officejet_Pro_L7500?zc=Printer
  1         hpaio:/net/Officejet_Pro_8600?zc=HP8F7B78


Enter number 0...1 for device (q=quit) ?0
warning: No destinations specified. Adding 'file' destination by default.
Using device hpaio:/net/Officejet_Pro_L7500?zc=Printer
Opening connection to device...
hp-scan[7586]: debug: Device supported resolutions [75, 100, 150, 200, 300, 600, 1200, 2400]

Resolution: 300dpi
Mode: gray
Compression: JPEG
Scan area (mm):
  Top left (x,y): (0.000000mm, 0.000000mm)
  Bottom right (x,y): (215.899994mm, 381.000000mm)
  Width: 215.899994mm
  Height: 381.000000mm
Destination(s): file
Output file: 
hp-scan[7586]: debug: Supported source Options: ['Auto', 'Flatbed', 'ADF'] size=3
warning: File destination enabled with no output file specified.
Setting output format to PNG for greyscale mode.
warning: Defaulting to '/home/pit/hpscan002.png'.

Warming up...


Scanning...

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