Hello bobrock,
A bit late response to your question, but better ever then never. I have the X-45 and up to a certain point, had similar problems. It looks like this... The throttle is build around sliding trims (for thrust operation) and vario pots'n'knobs (sorry but my English is not so adequate when it comes to technical stuff but I'll do my best). Over time, the sliding trims and knobs get dust contaminated, causing function interruption (God, my English sucks ).
Solution:
If you consider your self skilled do it your self - open the throttle (several screws and there you are), take an air compressor, blow out the dust, and then apply some contact spray or whatever you call it...
or,
take it to some electronic repair shop (like I did). They confirmed the dust contamination, sprayed it a bit so that it works like new!
Respect,
Sydious