Auto Transmission still sticking in 3rd

i have a 96 with the aw4 that has had an ongoing trans problem. It will randomly stick in 3rd or go into default. for those of you who have had similar problems, you can shift manually between 2nd and 3rd but 1st and overdrive are unselectable. it occurs at normal operating temp, and once the car is turned off for a minute or so and started back up it works fine for 20 min-2 hours while and then goes back into default. the trans is under warranty and the shop that rebuilt it assured me that the valve body and solenoids are all functioning properly.. they also replaced the transmission control module, throttle position sensor and tried many other things to solve the problem but it still presists. does anyone else here have a remedy for this problem? i haven't been able to take my rig out of town since june. thanks for the info

Can we assume that the fuse for the transmission control module has been checked/replaced?

the shop that rebuilt it assured me that the valve body and solenoids are all functioning properly

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Can't be.

the fuse is good