It would be nice to confirm whether you had the service at 100K miles on the tranny. Have you inspected the condition of the ATF and level? One word of caution is do not get a full power flush or fluid exchange flush with your mileage because it could cause more problems. Hard to say that is the problem but it is a good starting point since the tranny repair (solenoid only) could run around $500 - $800.
Also, a lot of us have tried adding trannny additive such as Lubegard, Lucas or Seafoam. It may help free up the sticky solenoid but no guarantee it will work. Good luck.