I'm not sure how a single inverter failure could drive voltage high. Or how a varistor failure could cause a problem... The inverter has to perform a DC-AC conversion and has many more ways to fail safe than unsafe but I'm not saying it is impossible. I've seen some oddball things. But it certainly isn't a widespread issue.
Smart meters report voltage, the utilities would know if this was happening and given how much they hate rooftop solar they'd be yelling about it if they could.
The problem is varistors blow out before the safety measures work. Perhaps due to wear or low quality, but this still happens.