AE is loading only every second frame

Hi!

I have after effect for a months, but this is first time i write here. I'm sorry for my english, but english is not my native language. I have an issues and it's that after effect only loads every second frame (so first frame is loaded but the second one is not, third is but next one not) what makes video kinda lagging and it bothers me. i cleaned the storage, tried to change some setting, but nothing helped. i didn't try reinstall ae. everything was still going well yesterday i dont understand that. please help. thank you for respond.