Hi, maybe old post, but I'm experimenting the same symptoms as @Nerdwarrior, cables were rechecked but my sensor sense ok till 60/70 degrees, then it start to fluctuate and reached the maxtemp error. Will check the block tomorrow, maybe I got the same issue.
But my question is that I searched the web but cannot figure where is the bed pt100 sensor located, cables are ok, but its on the block or integrated to bed? (didn't think it in the block ...)
Regards.