I think something like this happened to me when Yuna was summoning..yeah it didn't happen very often and just seemed to be a bit of a stall.

The only thing you should worry about is, what happened to me when I first got FFX, it played all the way up to the bit where Auron and Tidus first see Sin or something, then they would just stand there and tidus would keep moving but the game never progressed xD It was pretty annoying but I cleaned the disc and it was okay in the end