Hi kofi, I am sorry you made such bad experiences with the FP2. For me, however, I cannot confirm yours. Using “one of the first” FP2 since January 2016, I use it for business and private phone calls, E-Mail and Organizer (incl. Exchange-Server-Sync), pedestrian (and car) navigation, public transport navigation incl. the service offered by myself (e.g. by my corporation), internet browsing, banking, some music (stored on the phone and via UPnP), some guitar tuning, camera. The phone is not rooted, and I use only one SIM and no SD-Card. (There are many FP2 Users using SD-Cards without having update problems.)
Every system update went smooth, the known software bugs disappeared gradually. Some are still present, but not severe for me. For the battery draining problem I made some suggestions here as for several other problems as well, however the battery in general is rather week. The only hardware issue I had happened some weeks ago when I left my phone in my tent having direct sunlight through the plastic foil window. At 60°C or more, the rubber band of the case dissolved at the volume switch. The phone worked perfect even in this heat, but of course I had to buy a new case at the accessories shop. This one seems to be more reliable and looks even better.
So my suggestion, send your FP2 to Fairphone for exchange (repair seems not be enough), suggested there is still guarantee. There seem to exist some really buggy devices out there. But give Fairphone a chance to provide you with a working phone. I would be glad to hear from you here in this forum.