Dark themes are not consistentently executed on Linux Mint XFCE (22.2 Zara) #517

Hello there, I am new to this Linux thing and I have no idea if this is the right place. But in my new linux mint XFCE installation it seems, that dark themes are not persistent. Not sure if its a theme bug, a xfce bug or a linux kernel bug but I haven't found my problem with an online search and wanted to make the mint devs aware.

So I tested with multiple themes and it seems to be a consistent bug that when I choose a dark theme it will be persistent for thunar and most system apps but not apps like e.g. firefox (native) or flatpak apps like bitwarden.

Here are a couple pictures:

This is my firefox in a light theme ->

This is my firefox in a dark theme I like ->

And this is my firefox after restarting it (without changing the theme) ->:

The same is also true for apps like bitwarden (flatpak) and some other apps I tested. Again I am not sure what exactly the bug is and I am sorry if this is the wrong place. I also only tested on XFCE not sure if it also happens in the other flavours.