My interactive video is freezing at the same point, but only sometimes.

First time posting here. I've searched for other answers to this topic but haven't found anythign that helps.

I have a fairly simply interactive video, and sometimes it runs perfectly well and does everything fine, but other times it freezes at this same moment (frame 450, or really frame 449 since it is html5 canvas). The movie clip on the stage is still playing, and the music is still looping in the background, but the video isn't progressing.

There are some buttons that take you through the video on different pathways, and it seems that if you press more of them before this moment then the video is more likely to freeze, but it also sometimes freezes here even if you press the minimum number of buttons.

Whichever path you take through the video, you get to this moment by clicking a button with a 'gotoandPlay' action attached that takes you to frame 449, and then there is no active code on that frame, but for some reason it often just freezes there. 

Let me know if there is anything else I should add to this post to help folks help me. Thanks!