Subtitles getting cut off

I have a .mov file which is subtitled (created by someone else, not a professional video). I noticed when watching with Quicktime, every so often, the last word of a line isn't there. I don't think it's the length, because sometimes a shorter line loses the last word, and a longer line doesn't cut off.

I extracted the subtitles under Movie Properties and looked at it with notepad, and can't see any difference at all between the lines that cut off and the ones that don't.

The subtitles display correctly in VLC without being cut off, however every so often the text (NULL) shows up and when that occurs the entire subtitle is missing.

Any suggestions? I'm using these programs on a Windows 7 computer. Thanks!