I experienced some "reboot" yesterday and today thought my Phone has never rebooted till now. Today I had some time to explore some more knowledge and I write this down for the Fairphone-tech-team.
My OS: 1.5.1, the flavour coming with Google-Apps, but everything with Google in its name and some more (like Youtube) is deactivated. The phone is rooted, AFWall is active.
As location source I use "device only" - that is real GPS and it is always on.
I was on a journey and My web-connection was exceptionally "mobile data.
I have two SIM-cards in my phone with different networks and SIM 1 (E-Plus) is active for Voice, SMS and mobile data. It is set to "Preferred network: 4G". SIM 2 is set to GMS (Vodafone).
This morning I needed the navigation-app Osmand. The moment I tapped on "Map" the phone crashed. I tried it once again and "crash".
Remark on "crash": the crash showed the white screen of the phones normal start and then the loading-screen and a little bit black and then the lock-screen. Time from crash-start to lock-screen: about 10 seconds. But: no SIM-cards-PIN-query! So I think, it's not a normal reboot.
If I experience crashes of an app, I "force stop" it and clear the apps cache. On the restart of Osmand, same crash. Next: same procedure with the app and clear phones cache: same crash at tap on "Map". Next: look at the RAM: 1GB used, normal.
Perhaps another app: Satstat: tap and crash. Same procedure with clear cache and stop app and nothing better.
I have always the suspicion that it has to do with mobile data, because I seldom use them and have normally no reboots or crashes, so I switched mobile data to off and started Osmand again: it worked. Start Satstat: it worked. Stopped both apps, switched mobile data to "on", started Osmand and crash! I could reproduce this a few times. I even activated Maps and the phone crashed with mobile data set to "on". Everything was fine without mobile data. The connection at that time was H.
Next test: I brought Osmand to work and then activated mobile data: nothing, nothing, ... and one minute later: crash restart. Could reproduce this test too.
Half an hour later 50 km away and with a 4G-connection I had time again and made those tests once more: everything worked flawless ...
Edit 2 days later: could reproduce this again - mobile-connection-mode was weak H. Later with LTE everything was good.
Remark: my phone was never hot, but warm - as warm as a phone gets, when charging and navigating at the same time.
Edit 28.7. Had the same effect today with Open Camera: with mobile data enabled in H+ crash, without mobile data OK. Reproducible. 10 minutes later with mobile data at G4: Open Camera works.
Why Open Camera? The app is set to store photos with location metadata.
Everytime GSM and GPS get together the phone crashes.