I'm so sorry! At the time of first posting this mod, I had noticed this problem, and what the issue is is there's a hidden function that tracks whether you've gotten at least 20 points with the base romance characters at that point - which excludes Dominic for Max, and Sally for Anne. If you don't have at least 20 points with someone who isn't Dominic or Sally, then you will be forced to skip Winter Break.
I have recently found that function, however, so I can soon post the newly-working version of the mod if you don't mind waiting :) I'm so sorry!!!