Screen locks, videos pause, pages reload and screen turns black randomly

[AnotherElk]

@sarita

How can I solve my SIM issues? I use my second SIM card when I’m traveling for data (it’s a UK SIM). Any idea @AnotherElk ?

I don’t use Dual-SIM, so I have no experience with that. Some generic thoughts …

Try to put the second SIM into the phone again, perhaps this reseating already does the trick (seems to work for all kinds of cards now and then with a little luck)?

Try to swap the slots for the SIM cards.

@sarita

Unfortunately all the problems described above still continue in safe mode, so it seems that they are not caused by an app. What else can I try to troubleshoot? Or is the only option a factory reset?

If the fault lies with some malfunction of the OS, a factory reset might not fix this. A factory reset on the Fairphone 2 only deletes all Apps and user data, leaving the OS as is (it doesn’t get re-installed or anything).
Instead …

Installing the Fairphone 2 from scratch in case of failure / Komplette Neuinstallation des Fairphone 2 im Fehlerfall

Updates could go wrong, upgrades could go wrong, own experiments could go wrong, any given thing could go wrong … and the Fairphone 2 doesn’t boot anymore, doesn’t update anymore, doesn’t do any given important thing anymore. Updates können schief gehen, Upgrades können schief gehen, eigene Experimente können schief gehen, irgendetwas anderes kann schief gehen … und das Fairphone 2 bootet nicht mehr, updatet sich nicht mehr, oder tut irgendetwas anderes wichtiges nicht mehr. If even a factory …