I have flown two pairs of 9102's in two different planes. Typhoon 2+2 about 400 flights and Enigma 259 flights at the moment and I haven't had a single problem with any of the four servos. Maybe you have got bad servos..

I feel the 9150 is slow (on 4cell pack) and has only a few advantages in comparison to the 9102. So far I haven't tried the 9154's but I might get a pair of those next.

Has anyone used these digital low profile servos with regulated 6V power? I guess it is okay.