I have for some days tested Copter 3.5.0-rc9 with following problem.
When I loaded ver 3.5 into Pixhawk is't working fine, Load done, calibrating done
Next day I do autotune, well done no problems and a short test fly. No problem so far.
The I restart pixhawk, no GPS signal for next 1 hour, tried several thing, new GPS, same problem. The drone was put away for next day.
Next day I start the pixhawk fine GPS signal. Hmmmmmm.. After 10 min no GPS signal and for rest of the day.
Today I got the pixhawk out again, this was staying in 15 deg temp. Outdor temp was 20 deg. Now I restarted every 5 min. After 25 min no GPS signal, cont restart next 30 min, same problem. Hmmmm..
Reloaded without restart, version 3.4.6, restart Pixhawk, wupti GPS was bak, and I have now tested for 2 hour and it's starting every time....
Pixhawk is ver 1
Look like there timing problem in 3.5, when Pixhawk got some temperature....