There’s no indication that you have a solenoid issue. It’s more likely that the readings have come about as a result of the transmission going into failsafe mode. The question is, why?

How certain are you that your transmission is selecting 5th gear, rather than 4th? I ask because 4th gear is the default on the 5HP24 and this could be significant. If it definitely is 5th gear, then that would indicate a fault with your A-clutch.

Phil