Maybe of interest, apols if not...
I have a couple of wireless thermometers, purchased about 4 years apart, but otherwise identical. They display indoor temperature from an internal sensor, and outdoor temperature via a radio link from a remote sensor. One hadn't been showing the outdoor temperature for a while, and this morning I got around to investigating the problem.
It came apart nicely, just four small screws. Inside, I found a large pcb, obviously the main logic board, and a smaller board containing a crystal and some other bits, presumably the RF receiver. The smaller board was held in place by just a big dod of gloopy adhesive. Running beneath that board was a blue wire navigating its way around the interior. On cutting the adhesive and lifting the small board, lo and behold a solder tail had punctured the insulation of said blue wire. With puncture removed, normal operation resumed.
Of interest, upon disassembling the later version, the blue wire had been rerouted around the exterior of the board, rather than underneath it. In the one that broke, the blue wire was thus about 1cm shorter. I'm sure if there were enough decimal places in the world, we could work out that it actually saved some fraction of a percent on manufacturing costs.
I have seen this failure mode before, where a wire has been punctured or fractured owing to poor routing. Last time was somewhat more worrying, a plug-in automatic night light. With a bit more juice available from the mains transformer, that one had actually caused a proper little bonfire inside before a fuse blew.
