Hang on, Guys. Before developing theories about what makes it OK to go up can we go back to the basics.
Mr. Ed is right to wonder because it is not supposed to go up it is supposed to go DOWN during the mag check! (At least in the R22, R44 and the FWs I fly. No question about that.
So back to the original question - why is it going up?
Could there be a problem with the switch/wiring and it is not firing on both mags when you think it is and firing on both when you think its only firing on one?