Theme looks different with the latest Obsidian Update 0.15.6

[Flummic]

I love this theme, but I think the latest Obsidian has changed some things under the hood which make this theme look a little rough around the edges :)
For example when I click on anything in the sidebar it will add a white border around the element (screenshot):

Normally it looks like this (with no interaction)

For now I rolled back to Obsidian 0.14.15 and that seems to resolve my issues. But that's ofc only a temporary fix.
Sadly I don't know enough CSS to fix it myself :)