I tried to shoot a video for you to see but it flickers no matter what recording util I use (even tried ffmpeg). Anyway, I have tried KeePass 2.38 with a freshly deleted KeePass.config.xml (the only change I did was set the Lock workspace to 10 seconds and enabled that option). I can reproduce the issue any time and I tried it even on another VM (Ubuntu 17.10). I could record the video using VirtualBox if you need me to
For me it also locks when the dialog is open even in Mono. The issue occurs when you hit enter in the dialog to search for something. It can be any string (even if the item does not exist). After you hit enter to search and close the dialog, the locking will not fire up
Lock workspace after inactivity - not working in special case