My Etrex 20x, usually highly reliable, shut itself down 4-5 times on Sundays ride. Each time restarted okay, then turned itself off a few minutes later.
I swapped batteries mid ride, even though the installed ones showed two bars. That solved the problem for a few hours, then it happened again.
I use eneloops and an intelligent charger, although did have to replace my charger recently, so maybe a battery issue.
When I looked at the Etrex on my PC today I cleared out a load of archived files, but that still leaves only 318Mb free memory. Most of the memory is used by gmapprom which is 3.26Gb.
I tried comparing with my spare unit, but as it's an Etrex 20 (as opposed to 20x) it didn't have this file as the mapping is on it's SD card.
I'm thinking most likely a battery issue, so will try going back to my original charger which is now working again. Any other thoughts on possible cause & solution would be welcome.