Making a mission in San Andreas is very easy.
Making a mission in San Vice is not.

Here are the crashing problems

-Browsing too many skins
-Browsing too many objects
-Making missions too long
-Having too many objectives

TIPS TO REDUCE THESE CRASHES
-Don't use skins that are far away from each others according to IDs
-Use G and H for quicker browsing
-You can split a mission into two parts and then make it like a Mission Pack
-Use at least G or H or Y or N at browsing objects not too much,not even 8 times
-Use cars as an object. You can lock it,make it everythingproof and it's now an object.