The springs balancing the dishwasher door started twanging again, which I now know is the diagnostic sign that an asphalt sound deadening sheet has slipped off the tub. A sheet on the right side almost perpetrated a clean escape, but the flap drooping over the spring gave it away:
Another sheet on the left side was inching away, but hadn’t quite gotten over the fence:
They’re pretty much a rigid solid at room temperature:
It puts one in mind of the pitch drop experiments now running in various labs. In this case, we now know it takes about four years for an asphalt sheet to slide completely off the tub; those two sheets were definitely in place when I buttoned it up after the previous one broke free.
I applied a heat gun to soften the sheets, then smoothed them around the tub again. This time I applied long strips of Gorilla Tape from one side to the other, rather than short strips of ordinary duct tape along the edges, and maybe this fix will outlast either the dishwasher or our tenure here, whichever comes first…