It sounds like it might be the result of a floating point precision or rounding issue. SM2 keeps track of fractional seconds passed since the previous frame, and over time, I can see that possibly adding up. Though in all my tests, identical animations play in synch indefinitely. I'll give this some more thought and see if I can think of why this would be occurring and how to prevent it. If you could send me a sample that demonstrates this privately, that might help as well. Thanks!