I would give it a try. Sure, it is way better to find and eliminate the real cause. But in your case, I think a factory reset will make your Fairphone work properly again in a few hours.
Do not forget to back up your data first, especially the media folder!
Ha ha save me data on the SDCard that doesn’t have write permission anymore after the update?!?
Ha ha bis… that’s well said! 
For the time being I’m charging my dead phone… I’ll get back to you with stats as soon as I have them… where should I look?
You can use a data cable to connect the phone to a PC, too, to save your data.
You can either format your SD card and copy your files with Amaze to the SD card, or, if that shouldn’t work, simply copy your files straight to a computer (no need for a SD to copy your media files).
I know guys just kidding… by the way haha again as amaze dissappeared after the update! 
Correct, it seems to be no part of Fairphone Open OS anymore:
Looks quite good from my view, though I am no Android expert to make a judgement.
Edit: There might be one suspicious process I recognized now: “msm_ehci_host”
Do you use a charger that supplies ~ 1 A? (Even a powered USB hub might not supply enough power to charge the battery completely.)
I have to confirm this but this morning I check the “do not disturb” button on my (computer) sorry I meant phone of course… 
and CPU doesn’t get hot anymore (for the time being anyway) and battery prediction seems OK…
But I’m not sure it’s related I have to check it out more…
Do you mean the “airplane mode” in Android?
First of all I meant “phone” (not computer) of course…
No I have a “do not disturb” button… if you don’t it may be a feature of “gravitybox” it’s the one in the middle of the screen:
While I’m not an expert on this, I don’t see any abnormalities here. Yet, as you can see from the apps manual, it is suggested to charge the phone and leave it untouched for at least two hours to get meaningful readings, so I would try that as well.
You were right; it’s not gravitybox, it’s part of Android 6!
Which makes me wonder: how old is your SIM card? I have read reports that old SIM cards sometimes caused problems like overhearing or battery drain. If the problem returns, try to use the phone without SIM. Potentially changing the SIM for a new one may increase battery life, as that could be the cruel pit.
If you google for “GravityBox battery drain”, you will find a lot of reports about it.
You could uninstall GravityBox and see if your battery life improves.
I’m seeing some problem here :
your phone never sleeps ! its almost never in deep sleep !
i think the problem is related to your wifi, in your wifi setting ,deactivate something called like “wifi always active”.
I think the question here is: was the phone used or not. The period is only 38 minutes, that is a very short time.
I would recommend @evidemment to follow the apps guidelines on how to use it in order to be able to make a better judgement.
Maybe this is a good idea but I can’t imagine my phone without GravityBox…
No phone was not really used so staying awake that long is very very weird…
Alright, but who knows if GravityBox could be responsible for your WLAN being active all of the time or not? You can find out only if you uninstall GravityBox temporarily…
I don’t understand… yesterday morning CPU was not hot anymore and battery life seemed OK. This morning CPU’s very hot and battery life a disaster again…
Haven’t changed anything… seriously… exact same conditions.
I noticed though that phone is very slow to charge… I’m desperate…
