Anyone?

Where are the desktop wallpapers settings stored? I'm pretty sick of this bug and would happily hard-wire the wallpaper at this point...

Wrong product "Wallpapers shipping with Plasma 5" != wallpaper settings.

Moving to plasmashell

Do you happen to have Multimonitor setup?

is a symptom very multimonitor and if the version of plasmashell is really 5.5.5 is quite expected ( and should be marked as fixed)

Ahh, yes - I do have a multimonitor setup...

ok, it's not valid anymore after the rewrite during the 5.7/5.8 time
(if you want to keep an older but stable version i recommend 5.8 as is long term support)

FWIW I get this:

plasmashell --version
plasmashell 5.8.4
KCrash: crashing... crashRecursionCounter = 2
KCrash: Application Name = plasmashell path = /usr/bin pid = 2025
KCrash: Arguments: /usr/bin/plasmashell --version
Segmentation fault (core dumped)

I can confirm this problem is still current.

Can you please provide ~/.config/plasmashellrc and ~/.config/plasma-org.kde.plasma.desktop-appletsrc files please? also please provide output of "xrandr -q"

xrandr -q
Screen 0: minimum 8 x 8, current 3200 x 1200, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 connected primary 1600x1200+0+0 (normal left inverted right x axis y axis) 408mm x 306mm
   1600x1200     60.00*+
   1280x1024     75.02    60.02
   1280x960      60.00
   1152x864      75.00
   1024x768      75.03    70.07    60.00
   800x600       75.00    72.19    60.32    56.25
   640x480       75.00    72.81    59.94
DP-0 connected 1600x1200+1600+0 (normal left inverted right x axis y axis) 408mm x 306mm
   1600x1200     60.00*+
   1280x1024     75.02    60.02
   1280x960      60.00
   1152x864      75.00
   1024x768      75.03    70.07    60.00
   800x600       75.00    72.19    60.32    56.25
   640x480       75.00    72.81    59.94
DP-1 disconnected (normal left inverted right x axis y axis)

cat ~/.config/plasmashellrc
[KFileDialog Settings]
Recent Files[$e]=file://$HOME/photos/screen/m1.jpg,file://$HOME/photos/screen/m2.jpg
Recent URLs[$e]=file://$HOME/photos/,file://$HOME/photos/screen/

[PlasmaRunnerManager]
LaunchCounts=1 services_kde4-amarok.desktop,8 services_org.kde.kmail.desktop,3 services_org.kde.korganizer.desktop,1 services_org.kde.konsole.desktop,1 services_org.kde.kcalc.desktop
pluginWhiteList=services,places,shell,bookmarks,recentdocuments,locations,baloosearch

[PlasmaViews][Panel 1][Horizontal1600]
thickness=54

[ScreenConnectors]
0=DVI-I-1
1=DP-0

[Updates]
performed=/usr/share/plasma/shells/org.kde.plasma.desktop/contents/updates/obsolete_kickoffrc.js

Created attachment 104177 [details]
~/.config/plasma-org.kde.plasma.desktop-appletsrc

I can also confirm that the background reverts to some default KDE pattern on reboot or logout/login every time.

In the interim time is there anyway to hard code the background - swap a file or edit a config file directly to fix this?

I don't know what the problem was but after a system reinstall (unrelated problem) of apparently the same version of everything it works as expected. Thanks!