The 616 and 617.5 motorsdo have a number of balancer problems. The 240D usually has the bolts shear holding the lower belt pulley to the crank. These repair quite easy.
The other failure; the balancer, itself, falling from the crank is usually after a repair. It is also much more critical as the balancer usually removes some of the crank in its way off. The balancer should be a tight fit and we use a factory tool to pull it on. If the pulley slides on or is turnable (without alignment dowels)by hand it will have future problems.