every time I use rotobrush 2.0 and move forward one frame after effects crashes

downgrade  os to 11.2.3 and all working 

Without any info on your project, your footage, your computer, your RB settings and so on that doesn't tell us anything. You need to be more specific. Start by verifying that your source footage isn't damaged and also that your hardware acceleration is working as well as your disk caches.

Mylenium