tranny slipping into n Options

[Malhar95]

Posting this for a buddy:
It's a 7a auto 1994 (corolla though)

The tranny keeps slipping into n after driving it,
It did before 2 weeks ago, checked the fluid it was low, then after a qt it showed too much but when we pulled the drained plug it pulled only a qt out (so dip stick might be bad) then it was normal driving fine

Today the car went into neutral suddenly, fluid shows fine.
Should we drain and put new oil in since dip stock can't be trusted or could it be something else?

I remember similar thing happened to my celi but it was something to do with shift cables..

[Smaay]

are you checking the fluid with the engine running? thats how you so auto trannys