I dont know why but a just had a bug when I was drawing simple Mask on png files, at one point the composition frooze, I couldn't preview it.
All other comps worked fine. After a while After Effects frooze too, restart did not help, frooze everytime I opend the project.
If somebody encouter this problem. Delete the footage file you working with so it looses the connection to it and than copy all work from this comp in a new comp and relink the footage file. Hope this workaround can help somebody not loosing their work
I don't know why this is not happening in the new comp with all parameters the same.
I think I don't have to mention that your making software more buggy with every update you roll out, right? You know this already