We have just pushed a patch release - Copter-3.4.6. This is a very minor change on top of Copter-3.4.5 but fixes a nasty arithmetic exception that could occur if the WPNAV_LOIT_SPEED parameter was set to zero. Release Notes are here and the change is:
- ensure WPNAV_LOIT_SPEED is non-zero to avoid divide-by-zero
In short, the vehicle would lose the ability to control it's position in Loiter if the WPNAV_LOIT_SPEED parameter was set to zero which is luckily not something that people do much. If this happened, the pilot could only recover in manual flight modes light Stabilize.
Thank you very much to "darcopter" who reported the issue on this thread including logs.