Wow, the number of display issues with KVM switches is huge:
google: KVM switch issues
And I even found one that causes missing menus:
google: kvm switch missing menu
https://forum.blackmagicdesign.com/v...?f=21&t=166728
And from reading up on them it seems the KVM switch most often the culprit in how it emulates to the OS that the monitor is still connected.