I have had the same hitec servos in my 100cc yak since 08 and not a single issue. I have seen every brand out there cause crashes, nothing human can make will ever be perfect and not have defective items.
ORIGINAL: SinCityJets
It has nothing to do with the powerjack. The only thing the PJ does is LOWER the voltage going to the receiver. It does not AMPLIFY the voltage to the servos....one of two things going on here:
1) The voltage is not set right on the regulator
and / or
2) Welcome to Hitec servos......I lost 4 of them (at different times) on my 40% AW Yak.....bye bye. Back to another trusted brand.
Chad