Just had a similar noise/problem with W124. Started making a metallic knock on bumps. Started quickly, was not like a slow problem developed. car still handled well.

Sounded like the left front so took a look under and the front inner sway bar mount was gone. Not the metal bracket (that was still there) but the rubber bushing was gone.

On closer examination the bushing had split in two. Most of it was on the bar between the inner and outer mount, the other piece was on the bar on the inboard side of the inner sway bracket.

Easy to replace. The outer is held on with two 13mm nuts - the studs are permanently mounted. The inner is two 13mm nut/bolts. They are self locking nuts so a bit of a pain to undo but no big deal.

Hints - have some channel locks handy to compress the clamp when you are putting the new bushings back on, You can get one end on easy enough but I couldn't compress it by and and used the channel loks on the end of the clamp to bring it close enough together to get the nut on (You'll understand if you do it). On the outer bushing put the lower nut on first - there are two edges you can grab on the upper to do the compressing (nothing on the lower)

Good luck