I tried with everything - this is a non modified version of your theme that its happening on, not the original toolbar (the grey one) - Only happens on 4k screens with "zoom" - tried on two different computers. Natively 4k works, but of course thats impossible to use.
I added screenshots of different resolutions below.
The names represent 4k how many percent zoom, the ones with 1080 show 1080 with how much zoom.