Oh, and I'm using the Thinkwise default theme...

Hey Onno,

I think in your theme there are some minor errors that cause this issue. (SF 2020.1) 

With the new SF some changes have been made (possible) in Themes icluding changing the Tab height. See:

Results in:

Possible solution:

Let me know if this solves it for you!

EDIT: I see your comment new that you use the Thinkwise theme. In there it states Default and I'm not sure what it means. Maybe there's another way to to adjust the Tab height that I'm not aware of. You can try using Spacious, it helps for me.

Kind regards,
Mark Jongeling

Thank Mark, it worked.

 I think you selected your own answer as best answer.

Sorry Mark, of course YOU are the KING...