APM settings disappeared

Not sure which sub forum to post this since I don’t know if my problem is firmware, software or hardware but this has now happened twice to me where my APM has gone back to initial firmware state. Its as if I just downloaded 3.1.5 and not done any setup.

Two days ago my quad with APM 2.6, v 3.15 was flying beautifully, running auto missions and taking photos using the “auto waypoint-survey grid” feature with up to 82 command lines (approx. 40 waypoints). Then yesterday I did my pre-flight checks, uploaded a new mission with 218 command lines (approx. 119 waypoints) then attempted to read the mission file back to mission planner to verify it wrote correctly to APM. The mission would not read correctly from APM, it appeared to read but then I got a blank screen. Then my quad starts beeping and Mission Planner says “Prearm - RC not calibrated” Ohoh I have seen this before and posted here (viewtopic.php?f=12&t=7032) in the mission planner sub-forum but got no answers. At that time it was using Mission planner 1.2.95 and Arducopter 3.1 but now the exact same thing happened.

Now all my settings are gone, all PIDS and all of the setup calibrations. In both cases it happened when uploading and then downloading a mission, but I do this lots, as part of my standard operating procedure. In both cases I was uploading larger missions, the first time it was with 164 command lines (approx. 85 wps) . is that it? Am I exceeding the memory limits and wiping out the memory? I wouldn’t think so but the only other thing I can think of is if its an APM hardware issue.

I have about 6 logs on the APM from prior to this happening but nothing from yesterday, probably since the quad was never armed.

I sure hope someone can help with this but I have not seen anyone else with this problem. I am supposed to do some photos this weekend and will setup my spare APM2.5 but I am nervous as hell.

Thanks, Dean

No suggestions/answers as to what I am experiencing here? Is there a limit on waypoint/command lines that one can upload to the APM? There must be a limit but I certainly can’t find it in the Wikki or anywhere else. If you hit that limit does it actually corrupt the EEPROM or just not upload the mission?