[Mazyar Sharifian]

I ran into the same problem and I realized that it is due to framerate change.

I had a text layer in a 25fps comp which was a subtitle for a feature film.

Then the client requested a 24fps version of the subtitle for cinema premiere so I copied the text layer from 25fps comp to a new 24fps one.

At first I didn’t have any problems, but later on, when I arrived at around 45 min, the mentioned problem happend.

Solution:
The solution is simple. Just create your layer from scratch in a comp with a correct framerate (In my case, a text layer in a 24fps comp), then copy the attributes (Effects and Keyframes) from the one which is locked to the new one and then replace the new one with the old one.