Hobbywing ESC start up issues

Align 500xt. stock servos and align BL80A (previously futaba s bus )360 flights never crashed.

during these 360 flights probably 5 times the start up has spooled the blades around nice and slow for the first few turns then it goes crazy flat out and turns the heli on its skids a bit, so long as you were zero pitch it was no great shakes just woke you up a little. I recently changed to Jeti, and changed the esc out for a hobbywing 120a, due to the spool up issue.

throttle connected to receiver directly.

I set store gov and initialised the first flight 0 degrees, all good. first few flights perfect. slow spool up nice, i have 5/6 of these hobbywing esc, but this heli on the 3rd spool up turned the blades maybe 3 times then just went full bore, killed itself on the spot, probably turn 5/6 was the boom strike, it blew the gears one way bearing all the blades, swashplate, big mess my only difference was i had enabled telemetry.......which was working...(no auto bailout set as its a 500) Any ideas? Much as welcomed as its shelved till someone can Help Solve the mystery..