Lock up stops working when hot?

[NCTTA]

I have a FAST system with the lockup on a switch. Lock up works fine untill the tranny gets hot. If it is lock when that happens it take about 2 min to unlock. If it is unlocked it will not relock until the car cools completely down. The tranny was receintly converted back to lock up and is working fine otherwise. I just install Bruce's TC solenoid but that did not cure it. What are my other possible problems? Brake switch works fine to unlock until the temp starts the lock prob. Atleast I assume the temp is affecting the lock/unlock.