I have the some problem with my 75 240D, the steering gear box design is similar with the 123's. The frame where the gear box is mounted have some cracks and it was repaired. I have a body shop weld a small plate over the crack area, but it only lasted two years. At this time, I check and tighten all three bolts once a month. If the bottom bolt slip off the socket, I know the vibration have loosen the bolt too much, and I replace the bend bolt.

jack