And now for the anticlimax: after an e-mail from Monsieur Lurne, I realised what the problem might be, and simply washed the belt with warm water and washing up liquid, cleaned a little the pooleys, etc., and the arm works again as wonderfully as it did without fail for the last 11 years, since I bought it. The SL5 is simply a superb linear arm, which costs only a fraction of the price of the great names, yet has all the advantages of linear tracking. In any case, good "hygiene" seems to be a requirement of all linear arms, no matter how exotic or expensive. By the way, I am not connected directly or indirectly with Audiomeca or Monsieur Lurne, and have never been there, nor met him. Now, if you are familiar with the SL5, I would be interested to know what cart you would marry it with.