Possible reasons:
Mechanical problems:
* Wear of friction discs
* Torque converter problem
* Faulty gear shift solenoids
*Transmission housing problem
Fluid problems:
*Low transmission fluid level
* Contaminated transmission fluid
* Incorrect type of transmission fluid
Electrical problems:
* Malfunction in electronic components of the gearbox
* Wiring problem
Software problems:
* Malfunctions in the transmission control unit
Other possible reasons:
* Faulty engine or transmission mounts
* Cardan shaft wear
* Slipping of friction discs
Diagnosis and elimination:
* Check the level and condition of the transmission fluid.
* Determine the presence of fault codes using a scanner.
* Visually inspect the transmission for leaks or damage.
* Check the functionality of the gearshift solenoids.
* Measure the pressure in the transmission system.
Repair:
Depending on the cause of the problem, you may need to:
* Replacement of friction discs
* Repair or replacement of torque converter
* Replacement of gear shift solenoids
* Repair or replacement of gearbox housing
* Transmission maintenance (fluid drain and replacement, filter replacement)
* Repair or replacement of electronic components
* Troubleshoot wiring problems
* Transmission software update
* Replacement of engine or gearbox mount
* Repair or replacement of the driveshaft