@couet It seems to me that this is a classical problem of "blocking I/O” (the same as in the thread I mentioned in my previous post).
@rraut If you do not want to solve it properly, you can try a “brutal fix” (which may or may not work) … after the last “Update” call (and / or before you start to wait for user’s input), add:
gSystem->ProcessEvents(); gSystem->Sleep(100); gSystem->ProcessEvents(); gSystem->Sleep(100); gSystem->ProcessEvents();