Well, turns out the problem was that it was all towels in that first load. It's now working fine with an ordinary load. \towels too wet and heavy, I suppose.
Well, my dryer (Classixx7) has exactly this problem and it is brand new -- it was delivered yesterday and I tried it out for the first time today and after a minute or two it switches off, container and start light flashes! It can't be sludge, being brand new. I called their services and the...