Sounds like a bad gyro or you end to end travels are binding the slider to he extreme sometimes. You have to back off total travel so the slider does not bottom out. If the servo was bond over to one side and releases when unpluged could be that the gyro at rest is moving the servo to one side and that is nornal for heading hold. If you are using FM/PPM receiver than I would say you got a radio glitch. I had that happen twice. I went to PCM and then on to 2.4 with no further problems.

Don't down grade your EXI it is fine. Take that money you saved and up grade your radio/heli/gyro/servos or take you lady out to a nice dinner and if the Trex boys want to make fun of your helicopter just take note that most of those posting don't even own one or have been in the hobby long enough to know the difference.

Just take everything as suggested by the guys one at a time and you will work through it. You may want to move some of you radio gear around. I want my gyro and receiver as far away from the motor or ESC as I can. Check that pully again. It may test ok on the ground but in flight they could heat up and the tail shaft pully and /or front pully can spin on the shaft. Front pully if it is plastic needs to be CA to the shaft or replace with a metal up grade. The Trex SA was known for that that problem. EXI is a SA copy.

Good luck,

Jim