07-20-2021, 07:31 PM
I have always thought it to be a combination of corrosion and mechanical movement. The nichrome can get super hot. Expansion rate is 14.0E6 + or - %10 (so says google) but the contact point with the tinned copper terminal, while being a heat sink, is probably going to have some ware/ expansion in that contact area. A crimp with some plyers SOMETIMES fixes it.