there are threads already on this subject, but for every final fantasy i've played on my playstion one if I have problems with the movie sequences I pop open the playstion lid and leave for a few seconds then I put the lid back down.
It will skip the movie section all together, I tend to do this on disc 3 on ff9.
Failing that get yourself some scratch remover and apply it to the disc it may help your game work better.