[Bigmango]

The debugging output actually shows that the QT version is crashing on exit (window closes but process remains in process list, as explained).

Here is the strace output as soon as I select File>Exit (starting with --- SIGSEGV):

munmap(0x7f01ec0a1000, 32768) = 0
msync(0x7f01e67f0000, 10547304, MS_ASYNC|MS_INVALIDATE) = 0
munmap(0x7f01e67f0000, 10547304) = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=NULL} ---
rt_sigprocmask(SIG_UNBLOCK, [SEGV], NULL, 8) = 0
mmap(NULL, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f01f51ba000
mmap(NULL, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f01f51b2000
write(2, "An unhandled exception occurred "..., 54An unhandled exception occurred at $00007F01F392425C:
) = 54
write(2, "EAccessViolation: \n", 19EAccessViolation:
) = 19
write(2, " $00007F01F392425C\n", 20 $00007F01F392425C
) = 20
write(2, "\n", 1
) = 1
write(7, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x2826ea8, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x2848270, FUTEX_WAIT_PRIVATE, 0, NULL

And if needed, here is what gets added to the last line (after NULL) after I terminate the process in the task manager:

futex(0x2848270, FUTEX_WAIT_PRIVATE, 0, NULL) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=2609, si_uid=1000} ---
+++ killed by SIGTERM +++