Assuming it is the same or similar to the w124, is there a chance that the motor is mis-aligned? Also, do you have the wires in the right place so they aren't pinched? Is there a chance you have the clamp reversed in the plastic base? One of the w124 DIY instructions showed it the wrong way around in one of the pictures.

I just went through this on my w124, and that clamp re-attached pretty easily (I gripped it with needle nose pliers to clear the lip without too much force to possibly crack the plastic). So that makes me think that you may have something aligned slightly off.

Good luck.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).