i had the same problem with my '94. it would drop from high gear to a lower gear after warming up. they thought it was the solenoids or the fluid. it was neither. after dismantiling the unit, it was found to be a defective second gear clutch pack.
the problem was that we couldn't find the parts to repair it. after two months of multiple acura dealers searching in vain (we couldn't even find a new transmission), acura of tempe, arizona found one at the acura remanufactured warehouse in japan. i purchased it and had it shipped back to orlando and installed it here.
they said the transmission fluid was burned and that caused the failure.
i change the tranny fluid now with every other oil change (6,000 miles) and i haven't had a problem since.
good luck with your repairs.