Animating in photoshop help urgent!

I have this problem suddenly when animating in the timeline. I'm using the video layers rather than frame by frame animation but now suddenly frames 4 & 5 in any document will repeat what is drawn in either one. So if I draw something in 4 it'll show up in 5 which is really annoying because it means I cannot stop that bit from looking choppy. this pretty specific and I've never ever had this problem until today so if someone can provide an answer I will be so grateful. thanks