I built a F450 a while ago. I am using a Naza V2 and 90% of the time all is well. I do have some odd moments I cant easily explain. Most of the time it flies perfectly fine then suddenly in GPS mode I loose the ability to go forwards,every other direction works fine but if I try to go forward it tends to drift slightly to the right. If I switch to ATTI mode I have full control and all is normal,flick it back to GPS again though and it goes full speed backwards,again flicking to ATTI gets me full control back. I have landed and reset the home position and all is well again for a few minutes before it does it again. I had previously flown two full batteries and then this started half way through the third one. This has happened a couple of times before but I shrugged it off,now it seems to be a bit more common. Irritating more than anything!