The pack/head combo I've heard the most negative about in terms of safety is Novatron...
I was a warranty service station for Novatron. I can tell you that they're every bit as good quality as the other professional packs. Top quality parts.
One problem may result from the fact that Novatron has a greater penetration into the amateur and casual shooter market, so packs are more likely
to sit unused for an extended period of time as compared to those that are used every day in a pro studio.
“Wise men talk because they have something to say; fools, because they have to say something.” - Plato
For as long as I have been in photography (>40 years), flash manufacturers, of both studio flash and speedlites, have been recommending reforming the capacitors on idle units at least 6 mo. intervals, plugging them in (if AC powered) and turning them on (AC or DC powered) for 1 hour.