This happened a few month's ago on my 89 300e, when I removed the rear disc a couple of springs fell out on the floor. The handbrake shoe retaining springs had broken allowing the shoes to lean on the back of the hub.

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87 w124 zender 3.6 - 3.0 kompressor in progress!
96 w124 e300 diesel - slowly being modded
98 w208 230 kompressor - m103 testbed SOLD.
96 s124 om606 superturbo diesel 508bhp