I have read somewhere in the past that a prop that repeatedly stops vertical on a 4 cyl engine, is very likely indexed wrong to the crankshaft. Is this true? Reason I ask is, one of the 172’s at the flight school seems to be this way. 9 times out of 10 it will stop vertical upon shutdown. It never occurred to me that it seems to happen more often on this particular airplane than on any of the others until I read about it, so it had me curious.