I think the biggest issue is the consistency. Sometimes they will call the slightest touch a foul, other times guys will mug another player and there is no whistle. It seems to change from game to game, and sometimes even quarter to quarter. They'll let them play physical for three quarters then all of a sudden its a tweet-fest.
I know the playoffs are expected to be more physical, but last night Breen made the point that guys get used to getting some calls in the regular season, then suddenly it changes in the playoffs. That shouldn't be the case. This leads to a lot of players complaining which leads to fans complaining and it just is a bad look overall.
I know missed calls are going to happen and they can't call every touch a foul (nor should they), but just call the game one way and stop handing out this "star treatment". When everybody in the building can see a blown call except the three guys expected to make the call, that's a problem.