This was reported by Aleksey Midenkov <firstname.lastname@example.org> on the gdb mailing list.
After starting GDB 9.1, the command "winheight src +8" produces corrupted display because the command window overlaps the source window.
Created attachment 12312 [details]
Proposed patch to fix problems with resizing TUI windows
Fixed on the gdb-9-branch branch.
The fix was not in 9.1, but 9.2, so fixing that.