I have seen dozens of balancer failures on MB diesels. I have seen two where the bolts were froze and the balancer spinning.
Both bolts broke on removal with a ten foot pipe.
The most recent one we quoted for a shaft removal and used shaft. From our experience if the balancer doesn't fit TIGHT to the crank, it will never work again. Our plan was to put in a used crank. The repairs would have been over half the value of the car.
The car was taken to a Volvo repair shop down the road and sat there for 2 months. They finally got it together and arranged the sale to the friend of the shop owner. The car lasted about 3 months and the balancer is back off worse than ever and the shop owner now owns the car and it is still sitting six months later. The car is history unless someone repairs it right and it doesn't get cheaper doing it poorly the first time.
We use MBs balancer installer as they fit that tightly. If the balancer can be installed by hand your in trouble.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician