This is awful. Stick to a unilateral course of calls: every match, every call, every ball, every player. Make a call, every single time, if the ball is 2 inches out or 20 feet out.
This happened to me not to long ago, the server decided to start calling his own serves when he got down in the match. Apparently, he forgot the rules too. Its not the servers call. Play every single ball until a call is made. Period.
This happens more and more in league play - you crush the weaker guys serve, they contend the serve was out. Its a joke and terrible gamesmanship.