99 4.2 with a trans that was rebuilt 6 months ago.

My truck has started giving a code for solenoid B and it randomly slips and then bangs into gear...only in 1st gear. Its as if it was in neutral and dropped into 1st. It feels as if it hunts when slowing to a stop also.
The solenoids been changed under warranty and it was fine for a week, but now I get the same solenoid B code and its slipping almost constantly, hot and cold.
Any ideas where to go from here? Could the valve body be damaged?
Thanks for any help.