When the Halifax Highlanders play the St John's Shamrocks, a Shamrocks player is shown wearing jersey #3. This would not be possible as #3 is Ross Rhea's jersey number which was shown being retired in the previous movie.
Headbutting an opponent is explicitly forbidden in hockey and would result in an automatic and lengthy suspension in any league, pro or amateur.
Doug misspells his own name when signing the form (he writes 'Dug' rather than 'Doug'). 38 mins in.