Very strange crashes with QSystemTrayIcon

Hello,
I don't think this is a Qt bug but I really don't know where else to post so please forgive me
I've had some really strange crashes in my application with the QSystemTrayIcon so I wrote a small test application to find out what's going on.
I have 6 testcases in my testapplication. To reproduce my problem you can just #define the EXAMPLEx stuff.
Case 1 crashes on Gnome and KDE with GCC (not with Clang, but Clang does not work in my main application, I have no idea why, it spams the debug console with a lot of slot not found messages).
Case 2: same thing
Case 3: This one works with GCC too, really creepy... But Case 6 does not, so it might be a Qt problem, not GCC.
Case 4: same as 3
Case 5 works with GCC and Clang on Gnome but on KDE the tray icon does not show up. I've seen a bug report about a similar problem but it was fixed about a year ago and I have recent versions of KDE/Plasma so might not be the same...
I've attached the test application.

Thanks for your time and have a great and bugless evening

P.S.
It crashes in the event loop, not in my code.