A likely reason is forgetting to change an array size or a "for" loop limit. Try a search of number 5 in your source code
Viewing post in Ultimate Sissy Simulator comments
it's not that simple, unfortunately. IDs are getting mixed up somewhere, and there's probably more to it. if it's not fixable as is, i'll quickly rebuild it from scratch. and since It's still in early development, and there's a lotta quick n dirty prototyping going on. i need to start fixing all that, it's starting to give me a hard time.