I have had the game crash while retiring a vehicle. This has happened to me three times.
It seems to happen when the vehicle is at a stop and waiting to be loaded. Not sure if this matters, but it appears to happen when I am deleting multiple vehicles.
I am playing version 121.0-r8870
Does the crash also occur in the latest version (https://forum.simutrans.com/index.php/topic,20389.0.html)?