Corkboard background won't change

I’m trying to change the cork board background via Scrivener Preferences/Appearance/Corkboard/Color tab. I just updated to the 3.1.4 version but I can’t say if t is related to the upgrade or not. This is the first time I’ve changed the background in a while.

I have a custom background (which is just a .JPG file). And no matter what option I choose (trying to change the freeform background) it won’t change from my current jpg image. I tried deleting any reference to that image on my hard drive, and even resetting all preferences back to default (ouch! but thought it might solve my problem––but no :cry: ).

Note also, Before the upgrade I had the standard background (however it comes out of the box), then upgraded, then went into preferences and changed the freeform background to custom, selected my JPG file — that worked. But now I can’t get rid of it.

Is there something I can reset to get the corkboard background to change again?