firstly you are running a pre 2000 722.6 transmission. It has an aichelles heel in it, its the 2nd clutch bearing surface (a bushing - later replaced by a bearing in post 2000 transmissions)
If the pump goes dry, or works on overheated fluid that bushing goes out of round and your input shaft then wobbles, which does 2 things.
1 grind the planetary gear sets at the front
2 bang the impeller in the torque converter.
The golden rule to keep this transmission working is fresh compatible fluid with 30,000 mile intervals and correct level of fluid.
the other heavy ulfbehrt sword strike is the limp home mode in the 722.6 trans - no generic reader or battery disconnect clears it, you need the MB star software or something similar to reset it. Its pricey.
A general rule of thumb with this trans is to replace the electric connector bushing every 30,000 miles or so with a genuine updated mercedes part (which is cheaper to buy at the chrysler dealer
)