98' E430 wont shift gear
 

I recently bought a 98' E430 with 85K miles on it and it quickly started having problems with shifting gears. The transmission seems to be stuck in a gear and wont shift down or up. I could be driving it hard on the freeway and when exiting and stopping at a stop light it wont shift down unless I manually shift it down or turn the ignition off and on again. Also it wont alwasys shift up in gears. I have had complete tuneup of the engine as well as replacing transmission oil and filter. My shop suggested re-learning the transmission but the problem did not go away, so then they tested some more and replaced the throttle sensor. The transmission seems to behave much better now, but almost daily I have insidences of the the transmission not shifting up or down, but then when it wont shift I gently pull on the gearshifter and within 3 seconds it shifts... What is going on here? - mo warnings or error messages and no codes

Any clues would be appreciated