Auto Trans problems 1996 318ti

Any advice would be appreciated (other than someone saynig "take it to a shop")
In 4th gear I am not getting full lockup. I can move to neutral at
highway speeds, then back to 4th and the rpm's are where they should be. Then after 3 or so seconds the transmission seems to shift down a half step between 3rd and 4th gears. The fluid is good, no slippage. I think this is an electronic problem. Help!!!

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