560SEC 85 European, seatbelt handovers suddenly inop

Suddenly and without warning both seatbelt handovers stopped working. There is no mechanical action taking place at all and no sound indicating they are trying so not the typical gear problem. I have checked the fuse. It is good and everything else on the same fuse works. I know there are a numnber of relays for the handoversin the rear door panels. Are there any resetable relays or breakers? Is there a test procedure for determining which relay may be bad (one that can be performed by the simple minded)?

Thanks in advance for any advise you can offer.
Jon Campbell

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