Trouble Codes 700 and 730

My daughter's Honda recently had the check engine light come on. It was showing the above trouble codes The car has 165,000 miles on it but the transmission was replaced at 120,000 miles. She took it to a mechanic who replaced the transmission fluid because it was overfilled and dirty, and checked the shift solenoids, then reset it. The light came on again as she was driving home from college two days later. I took it to our mechanic who reset the light again. She's driven it from San Diego to LA and back and the light has stayed off, but when she leaves the freeway and comes to a stop, the car feels like it's in neutral for a couple seconds until the gears engage. It seems to run fine around town and only acts up after driving at high speed for an hour or so.

We replaced the trans fluid with clean fluid first. The temp gauge is normal during freeway driving. The transmission we put in at 120,000 miles was used but rebuilt. Is there an additive we can put in with the trans fluid that will help? Could it be one of the other components?

We replaced the shift solenoids, and the car was ok for a couple weeks. My daughter drove it back to college (3 hrs on the freeway) and it was fine for awhile, but the check engine has now come on again Same problem- when she was driving on the freeway and exited, the car seemed like it was in neutral after stopping at the off ramp. Help!