I took my old heads to a shop for shafts. They offered me Nippon 950, second hand, so i took those. The shop installed and put on new grips. After 2 days no use, i took 8i to range with mats and after 10 shots, head flies off. No especial reason, like smashing the mat.
Of course shop will fix that one. My big concern is all the other iron heads. How common is this problem, what is usual cause and most important, the probability that one day another head will fly off, and maybe hit the caddy? Seems a reputable shop but mostly in a language i don't speak. Lots of golfers in there though. I'll ask the caddy to stand off.