Sadly there's no easy way to debug that I know of. Here's a rough process of what you can do using the
bisection method:
1. Make a backup
2. Start by deleting half of your instances at a time (company of heroes 2/mod projects/your mod/instances)
3. If the mod crashes it is located in the undeleted half, repeat the process until you find the offending instance
4. If the mod doesn't crash it is located in the deleted half
The above only works if there's
one instance which causes crashing. If there's more then good luck.