The replacement 130SS that Amain provided for my shaky one has turned out fine so far. Perhaps they've fixed it for good. It's a shame they didn't really admit the fault with them formally and explain the problem and the fix that they've put in place. It would have certainly restored confidence.

Personally, even though they seem to have fixed it, I wouldn't buy another one and I just have a general reservation over the general protek quality given my experience with the servo. Some might see that as narrow minded but personally there are better reputed brands out there for the same money.