Cannot modify preview_image_url via a PATCH or PUT call

I am developing a workflow to update some of my bookmarks and at some point I need to make a PATCH call to set some values of the bookmark. I tried to both use a JSON body and a key:value one.

• setting title always works ✅
• setting preview_image_url never works (it stays null)

I tried several URLs (including ones local to Linkding), I tried previewImageUrl instead of preview_image_url, I see the call arriving to linkding (on its console) and as I mentioned, tile is chnaged so the general workflow is OK.
I also tried PUT - same result

I have no other ideas, has anyone managed to make a successful PATCH call on this key?