Resume fails when suspending laptop with headphones plugged in

This is Xubuntu 18.04.1, kernel 4.15.0-43-generic on a Dell Latitude 5580.

I've found that if I have headphones plugged in when I suspend the system (either by closing the laptop lid, or by using Whisker menu > Power button > Suspend), then the system does not resume properly. It appears that a full boot occurs: Dell logo appears, followed by the Grub menu, and after selecting the boot option and booting, I get a new login session instead of my suspended one.

I tried some combinations of booting, suspending and resuming with the headphones attached or detached. The 'yes'/'no' indicates whether the headphones were plugged in when I performed the operation. 'ok' indicates that the resume succeeded: after authenticating to xscreensaver, my previous session was resumed.

  Boot: no Suspend: no Resume: no Result: ok
  Boot: no Suspend: no Resume: yes Result: ok
  Boot: no Suspend: yes Resume: no Result: fail
  Boot: no Suspend: yes Resume: yes Result: fail

  Boot: yes Suspend: no Resume: no Result: ok
  Boot: yes Suspend: no Resume: yes Result: ok
  Boot: yes Suspend: yes Resume: no Result: fail
  Boot: yes Suspend: yes Resume: yes Result: fail

(Note: for each case, the suspend was done via Whisker menu > Power button > Suspend)

The common factor for failure is suspending when the headphones are plugged in.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-43-generic 4.15.0-43.46
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/pcmC0D0c: stevec 2490 F...m pulseaudio
 /dev/snd/pcmC0D0p: stevec 2490 F...m pulseaudio
 /dev/snd/controlC0: stevec 2490 F.... pulseaudio
CurrentDesktop: XFCE
Date: Sat Dec 29 15:52:34 2018
HibernationDevice: RESUME=UUID=e77712df-7257-41aa-8062-076791733f67
InstallationDate: Installed on 2017-12-12 (382 days ago)
InstallationMedia: Xubuntu 17.10 "Artful Aardvark" - Release amd64 (20171017.1)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 002: ID 8087:0a2b Intel Corp.
 Bus 001 Device 004: ID 0c45:6717 Microdia
 Bus 001 Device 003: ID 0a5c:5834 Broadcom Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. Latitude 5580
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-43-generic root=/dev/mapper/xubuntu--vg-root ro quiet splash nouveau.modeset=0 pci=nomsi iommu=soft resume=/dev/disk/by-uuid/e77712df-7257-41aa-8062-076791733f67 vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-43-generic N/A
 linux-backports-modules-4.15.0-43-generic N/A
 linux-firmware 1.173.2
SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-10-30 (60 days ago)
dmi.bios.date: 09/12/2017
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.6.4
dmi.board.name: 0FH6CJ
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.asset.tag: L05248
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.6.4:bd09/12/2017:svnDellInc.:pnLatitude5580:pvr:rvnDellInc.:rn0FH6CJ:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: Latitude
dmi.product.name: Latitude 5580
dmi.sys.vendor: Dell Inc.