Desktop wallpaper too small

I haven’t read anything about this problem so it can’t be very widespread, but for the past couple of days the wallpaper on my second monitor has taken to only covering about 80% of the screen despite being set to ‘zoomed’. The first monitor has the correct size wallpaper but it is a laptop with a much smaller screen. Prior to two days ago this setup has worked normally for years. The only problem I have seen which looked vaguely like this was caused by cairo-dock and was usually cured by switching off ‘shadows’ in its menu. However this is not the case this time since even if I boot without cairo-dock the wallpaper is still too small. I thought it was something to do with an update I had to libxfce4windowing-devel, so I have tried downgrading it but the downgrade command can’t find another version. I have also tried switching to libxfce4windowing from extra repo but that makes no difference. I even tried libxfce4windowing-git but that wouldn’t compile so maybe this library is not the cause after all. Another strange thing is that the right click menu on both screens are not working. So does anybody know anything about this?

Manjaro xfce testing fully updated, 6.7.6-1 kernel (but an older kernel still has the same fault) . inxi -G
Device-1: Intel UHD Graphics 620 driver: i915 v: kernel
Device-2: Chicony USB2.0 Camera driver: N/A type: USB
Display: x11 server: X.Org v: 21.1.11 driver: X: loaded: modesetting
dri: iris gpu: i915 resolution: 1: 1920x1200~60Hz 2: 1920x1080~60Hz
API: OpenGL Message: Unable to show GL data. glxinfo is missing.

Well I got the wallpaper back to the correct height simply by going into display properties and changing the resolutions there. I don’t know what changed them in the first place, because it wasn’t me. I still haven’t got the context menu back on the desktop, but that is not really a big deal I hardly ever used it anyway. I guess it is half solved then.