We make an (electronic) component that's used in these things. Reliability ppm demands from the customer were ridiculously strict in their proposed contract. My boss refused to sign it and they still placed the order for this customer specific part. I guess nobody else was signing either... There were some failures with the initial revision stemming from undetectable cracks in a ferrite we use. No manufacturer will guarantee those to be completely free from latent cracks or micro-fissures. So imagine if one of the several that are soldered into every power module fails. Some poor tech has to get into his rowboat, get out there, climb up and replace the module. :) If this sounds prohibitively expensive, that's because it is. During the FMEA I had first contact with micro-tomography which showed the cracks in these potted components. We ended up designing a new revision with simulation for thermal aging stresses priced in. Every single component goes through that and is re-tested after. No problems whatsoever since then.