What could have caused this? I was driving down the road at 50km/h and I bury my foot into the carpet on the throttle and as soon as the kickdown switch is engaged, the engine revs up radically without any action... if I let out the throttle the car returns to normal behavior...I can do it again all the time...But at anything less than full throttle the shifts are crisp and defined so I don't think the transmission is on its last leg...

What could have caused this? Before I noticed this I did some freeway runs where I put the gear lever into 2nd manually, and then accelerated from 100km/h to 180km/h in D while the kickdown switch is engaged the whole time....it went well and then after having the car parked for a few hours this neutral kickdown phenomenon happened.

It's a 1997 C36 with the electronic 5 speed....what are the most common cause to this? The transmission has just received service at a local indy shop...