This was reported by Aleksey Midenkov <midenok@gmail.com> 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.