>> I'm compiling Emacs master right now (on macOS Catalina) and have 
>> detected a couple of warnings 'assignment to free variable repeat-map' 
>> (one in tab-bar.el and one in window.el) Which I haven't seen before...
>
> I don't see any warnings, so please show the warnings you see.
>

I see them (and have seen them for a week or two), too:

In toplevel form:
tab-bar.el:2093:33: Warning: assignment to free variable ‘repeat-map’
In toplevel form:
window.el:10261:33: Warning: assignment to free variable ‘repeat-map’

Patch attached.