I have suffered with the crashing FP2 camera for some time, Fairphone sent me a replacement module last summer. I have tried the hardware-based advice, but the problem always re-appears. For me it appears to be a software issue.
I found that 3rd party apps could launch the camera when the stock camera app failed, and this would temporarily fix the problem. I concluded this is an Android problem, and so no point in replacing or trying to fix the camera module. Android 7 update made no difference and the camera has since got worse.
I found this advice online from Google via user Josh Hudsy at androidcentral.com:
"Go to Settings > Apps,Camera, and then touch Force stop.
Go to Settings > Apps, Camera, and then touch Clear cache.
Go to Settings > Apps, Camera, and then touch Clear data. Caution: Any data saved in this app will be erased.
Then restart your device without opening the camera or any other applications that use the camera "
I tried this last week and the camera has been great! Beforehand, the camera would mostly fail. Since I did the above, it has failed only once or twice for many launches over 4 days!
Hope this helps.