I'm having the same issue and contacted FP Helpdesk directly. The request number is the following for the sake of transparency - 164438. I've personally tried to limit my GPS heavy apps but it is still happening, less, but still happening. I haven't found the solution yet and hope the next Android update sorts it out.
Here's the reply from Martin:
You can try fixing the problem yourself with the following:
Some Fairphone 2 devices are suffering from an issue which we call random rebooting – the unplanned and unwanted rebooting of your phone.
We are really sorry that you received a Fairphone 2 which is having these problems. We are investigating this issue:
we know that there are two possible causes to this problem and we would like your help to identify the one affecting your device.
With the phone powered on, please remove the back cover.
Now hold the phone with one hand and with the other hand apply pressure on the battery and try to move it around its socket.
If this prompts a reboot, then we have found the issue. Please come back to us and let us know!
If trying to move the battery didn't cause reboots, then the problem lies elsewhere.
At this point we invite you to try the following advices and see if they can address the issue.
If this is not solving your issue and you still experience many random reboots,
we do not want you to wait any longer and we will replace your phone. Thanks a lot for your understanding.
Have you tried without any SIM card in your phone? We've seen some old/dirty SIM cards causing similar issues in the past.
Also, have you also tried in airplane (flight) mode?
With a previous software update we introduced improvements to the device stability.
Please make sure that your device is up-to-date (see our guided tutorial on how to update your Fairphone 2 and our
related support article if you need more help updating).
After that you can also try operating the phone in safe mode. If the problem continues, do the following to try fixing the problem yourself:
We would recommend to do the hard reset and just install the latest operating system (as the last option). Also check if the display is well connected to the core module.
All files, contacts etc should be transferred manually. You can do a backup, but if your play it back on your phone,
the software problems will be transferred again to your Fairphone. This issue that you describe is likely a software issue.
How can I reboot my FP2 in Safe mode?
How to return to factory settings on my Fairphone 2
Some of these problems appeared while some Facebook (messenger) app was installed.
Please once reinstall this apps and tell us if the situation improved.
Please also lower the workload of the phone to prevent shutdowns:
Especially apps that require GPS seem to cause shutdowns. Please only use GPS, when necessary.
Certain apps, accounts and features impact your battery life as well. A few ways to decrease your phone’s workload include:
Wallpapers: Choose a static image instead of a dynamic one. To select a new wallpaper, touch and hold a blank space on your home screen, and then tap Wallpapers at the bottom left.
Inactive apps: Uninstall the apps you don’t use. Go to All Apps, hold down the one you want to remove, and slide it to Uninstall at the top of the screen and release your finger.
Accounts: You can remove the online accounts that you don’t use under Settings > Accounts. Locate the account you’d like to remove, and then use the settings menu (three vertical dots) to remove the account.
Users (Fairphone 2 only): Remove unnecessary users by going to Settings > Users. Tap on the cogwheel next to the user profile that you’d like to remove and then tap on Remove user. Please note: the Guest account cannot be removed.
Touch vibration (haptic feedback): Turn off touch vibration under Settings > Sound & notification > Other sounds and disable Vibrate on touch.
Keyboard vibration: Go to Settings > Language & input > Android Keyboard > Preferences and turn off Vibrate on keypress.
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