94 BMW 318i Transmission Problem?

We replaced the engine in this car and it ran fine for several months. It then started dying for seemingly no reason. We took it into the shop they told us the engine was grounded incorrectly (to the transmission) and was burning out the transmission cable. Engine re-grounded, transmission cable replaced. Car drove for a few more months now battery will not stay charged and transmission is stuck in third. Battery is good (it will hold a charge if it’s not connected to the terminals), alternator is good, no shorts in the system. What can we look at next? Are these 2 separate problems or are they the same problem?

This is a automatic transmission? Standard parasitic draw test for the battery going dead problem.

Never saw a BMW automatic stuck in any gear,maybe others have. We never did auto trans repair at the Dealer,not even in mid-90’s, I have no diagnostic experience.

Have seen some shifting inhibit problems on early 7 series when throttle switch wiring incorrectly hooked up.