If you want to get it working again you could attempt a reflow as described in the following post (without any guarantees of it working):
There’s probably still a minority of devices affected, as people who experienced this issue have a much higher incentive to post here or contact support about the issue. For more reliable statistics about this we would have to hear from Fairphone themselves though.
Keep in mind that most of us do not work for Fairphone, so for any official responses you’ll have to contactsupport.
Still, I do not believe anyone planned for ‘sudden deaths’ to happen.
It appears the issue may be related to Qualcomm’s Power Managment Chip PMI632 as mentioned in the following post linked below. That’s something Fairphone could not have predicted when designing the Phone.
Either that, or simply the layout of the motherboard causing soldering joints to fail due to bending (which may be fixable with a reflow).
Unfortunately there will always be some issues that remain undiscovered before a device is released, as they take some time to manifeat themselves. But in a way things have gotten better with later models, simply because the FP4 and FP5 have an extended warranty of 5 years. Hence parts affected by such issues appearing after 3 years would still be eligible for free replacement.