Garmin 800

[Collonach]

My much hated Garmin has decided to lose a number of tracks, which appear as 0kB in the Activities. These include some records that I had uploaded to Strava, so their reduction to zero has been subsequent to creation. But this week's hilly ride has disappeared without any obvious trace.
Before I throw it a long way away, is their anything I can do, either to recover the lost records, or to reset Garmin to start anew, presumably losing whatever should have been there? i.e. Do a reset.
I am trying to steel myself to buy a Wahoo Roam, but I would rather not do that for a month or so.

[Phil W]

My Edge 500 used to sometimes tack one days ride onto a previous days fit file. I sometimes found tmp fit fragments if browsing GPS on PC. So possible places to look but be prepared to shout f*ck once more.

[Feanor]

My 2 edge 800s have done this, and every time it has been when I have connected it to an Android device via USB-OTG and its tried to draw power from the Android device.

My tablet refuses it, and complains about a High Power USB device. The phone accepts it, but seems to corrupt the filesystem more often than not.

Perhaps a USB-OTG cable with external power provision might work better.