If I remember, during use, the rear bow comes down rather quickly. Perhaps something came out of adjustment and the rear bow now "bottoms out" in the folding top case, causing a jolt.

I'm not sure what determines the speed at which the rear bow falls. I thought it was something regulated by the hydraulic cylinders. Perhaps one or both of the cylinders are leaking internally.

Any external leaks?

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95 E320 Cabriolet, 169K