If you are in custom campaign mode starting a custom campaign and press F6 or try to use the normal save function, the game leads to a instant crash. I thought this bug has been fixed some months ago, obviously it isn’t the case… Has anybody else this problem?
A quick workaround can be:
1.) Delete the cache of the Battle.net app
2.) Delete the registry entry “warcraft3.save”
3.) Uninstall the game and install it anew
= DOESN’T WORK
But it seems to be a problem which is caused by Reforged! Any other user experiences are extremely welcome… 
Custom campaign: https://www.eredalis.de/warcraft-iii-the-frozen-throne/heroes/human/
Game version: 1.36.0.2.20257 x86_64
System: PC