Any particular window controls you're interested in?
"SyncTERM is not responding" modal dialog - Ubuntu Linux
Likely fixed in git now.
Also, why X11 and not Wayland?
I'm not sure what a "non-active desktop monitor" is... one without the mouse cursor on it?
This is actually from the gmake system using g++ as the linker... basically it's an artifact of supporting GNUmakefile builds. The CMake builds shouldn't have that issue.
Error Decrypting BBS List - MacOS Tahoe 26.4
Syncterm 1.8b ansi problem with Slackware64 15.0 Linux