Well, just mux any audio track with a 5 digit delay value and voilą, it will crash gMKVExtractGUI as soon as you drag & drop the resulting file in the gui.
I found out some other interesting weird stuff looking at this. Not related to gMKVExtractGUI but interesting.
See how MPC-HC starts messing up with how it displays the ac3 specs with a delay value higher than 7487.
No delay:
A: French [fre] (ac3, 48000 Hz, stereo, 192 kb/s)[default]
Delay value of 7487:
A: French [fre] (ac3, 48000 Hz, stereo, 192 kb/s)[default]
Delay value of 7488:
A: French [fre] (ac3, 48000 Hz, 2 channels)[default]