Folder background color not changing

[Rhea]

This is a wierd one so bear with me,
I realized after adding some new folders to my collection that the default folder background (the yellow folder icon) started to appear besides my recolored ones.
A while ago I tinkered a bit with the design of them and found out you could colorize those with a few line changes in the .ini/.css files:
viewtopic.php?f=82&t=38675&p=155786#p155786

So it seems that probably that folder style got disabled in a previous version release and I didn't realize because my older folders still got the outdated thumbnails attached to them when it still was working. The folders colors are modified with "m_folderColor(1-5)= " in the .ini file.

I tried different versions and could narrow it down to Win 0.98.2 64bit (Feb 19 2021) as the last working one. The change seems to be affecting Win 0.98.3 64bit and newer.

Any chance that something got changed by accident? I Couldn't find anything specific in the changelogs.
Probably I'm the only one with that problem, but at the moment I'm sitting on the older version and hope it could be fixed

-Rhea-

[xnview]

could you try to select the folders, and 'View>Rebuild thumbnails'

[Rhea]

I did that already, that's why I was able to even find the working XnView version:
After I realized the new folders weren't getting the supposed colored ones, I took a bunch of folders and rebuilt them with the "View>Rebuild thumbnails" function. They all ended up with the default icons, so I started to go back to previous versions to look if it was on my end in the config files or a change that happened somewhere in the releases. Everytime I did an installation, I rebuilt those folders (and even random ones didn't matter) to see if it would work.
A few installations later I suddenly found a working one and worked my way through the newer releases. At version Win 0.98.3 64bit it seemed to stop working, so I went back to Win 0.98.2 64bit to confirm. Even on a second device I could reproduce the same scenario.

So basically, if I stay on that specific version it works fine - but if I go for a any newer one it breaks. You can reproduce it by going to the Win 0.98.2 version and change those values in the xnview.ini file:
m_folderColor1=255 204 153
m_folderColor2=153 0 76
I don't know anymore why those two specific are responsible for the color changes and not the other 3 lines, but those two change the top half color of the folder (Color1) and the second half color (Color2). Together they create that gradient color folder, I even changed it to few other colors just to test if it still works (-Attachment-).

That color setup could actually be useful for XnView in general as I saw a few mentions in the past threads of "custom folder icons" instead of the default yellow one. Thumbnail background/border already can get color adjusted in the XnView settings menu itself, the folders to be customizable would be pretty nice as well.
viewtopic.php?f=60&t=37210
viewtopic.php?t=30262

If that whole thing is of any help