Hi people looking for some help I am new to the group also new to phantoms I purchased a f240 from eBay for some reason I didn't read the discription which normally I always do I only checked when it came and noticed it said it had a intermittent fault which I asked the seller what it was his reply was well I crashed it and replaced the shell sometimes the motors come on sometimes they don't which I have noticed I took the shell off and checked for splits on wires looses wires cracks on the board but nothing everything looks fine when it does power up it flys well but when it fires up one motor struggles when the rest come on almost like juddering but after about 3 seconds it turns on and maintains its speed with the other motors could someone please help sometimes it doesn't find a GPS either checked the cermatic patch that is fine has had a new compass lead as there is a spare in the box I've done a firmware update last night the only thing I could see on the board was dust would yous recommend wiping it down ? Thanks