There are so many variables that can affect the GPS lock, it's very hard to know the cause of a sporadic loss of signal. However, here are a few tips:
1) An important part of a GPS lock is the "Almanac". The Almanac is is a database with info on the satelites, trajectory, general health of the network, etc. The Almanac is part of the GPS feed, and all GPSes automatically download this data anytime you are receiving a GPS signal. If you're GPS has been turned off for a couple weeks, you may need a new Almanac, I suggest you power up your iFly 30 minutes before flight and just let it sit there and get refreshed.
2) Here is some background on the different Reset options:
- "Warm Start" or "Hot Start" (available from the GPS Diagnostics app)- forces lock to re aquire, but will use last known position. If all else fails, try the Hot Start option in flight.
- "Reset GPS" or "Cold Start" - this will cause the GPS to forget any cached information about your position and start from scratch getting a lock. It also verifies accuracy of current almanac. You should not do this in flight, as aquiring a lock while in motion is a LOT more difficult than getting a lock while stationary.
- "Factory Reset" - this causes the Alamnac and last known position to be flushed. It could take 20 minutes to reaquire. You should not do this in flight either.
3) Low voltage, RF noise, shielding, etc, can affect the lock. If you have an external antenna try repositioning that. If your lock doesn't return in a minute or two, try the Hot Start option.
4) If you are having this issue and don't have an external antenna, you should consider getting one. Or get an ADSB device, then you have weather and a backup GPS receiver.
Hope this helps a little,
Walter