I did check both the transmission and the engine mounts, and they all seemed to check out.
I did replace the transmission output shaft bearing and the bearing halfway down the driveshaft, so it seems to me that there has been some problems in the past with the driveline.
Does it make any sense that the torque converter has a bad bearing or bushing, thereby creating a vibration. BMW did have a bulletin out mentioning a failure here.

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