Just for kicks, take your antenna wire out of the plastic sleve! I have had glitches when the antenna is in a sleve. Run your antenna completely out in the open underneith the plane or top of plane. Has any of the antenna wire been exposed outside of the sleve? Are your linkages tight? ARe they heavyduty 4-40 rods? If not, they should be. You are upgrading your 605s, are these old tired or new servos? Do they have "play" in them? Im sure they are new, but just curious. Where are you testing your engine/plane? AT the field or a different location that could be prone to hits? If you change to the PCM receiver, you may get rid of some of this, but you best be careful! From what I have seen, PCM sometimes will mask a problem where FM will not.