Oil drips or dampness by the electrical connector on the side of the pan, a bump on the downshift just before stopping, harsh or flared shifts (especially 3rd-4th and 4th-5th under throttle) and a limp mode that clears after restarting.
Possible cause described
The sealing sleeve between the mechatronic unit and the wiring harness has O-rings that harden and let oil out. A BMW bulletin says to replace it only for a real leak, not mere dampness, and warns that fitting it wrongly damages the connector pins and forces a mechatronic replacement. With low fluid the gearbox loses pressure. Harsh shifts can also come from worn solenoids or valve body, not only the sleeve.
Check for the garage
At a garage: read the gearbox codes, check the fluid level with the official procedure (correct temperature and engine running) and look for a real leak at the sleeve and pan gasket. After a fluid or parts change, the garage should reset adaptations. If limp mode persists, check solenoids and valve body before replacing the gearbox.
Cost cited in the source
Sleeve and pan gasket: minor repair. If fluid is lost and the gearbox is damaged, in a US forum case BMW offered a remanufactured gearbox for about $2,800 without fitting.A rough figure from the original database, not an up-to-date quote.