In my case Camera MX solved these problems too, but only temporarily. Not a single streak in my pictures since the beginning of March. Perfect, but …
… some days ago - I updated it from 3.4.202 to 3.5.001. And the streaks returned. Downgraded Camera MX, tried other camera apps, played with all their settings. No success. The streaks persisted. I changed my camera app back to Open Camera.
Thought I’d have to live with it until the next Fairphone Android update.
My FP2 is rooted. I mainly did it to mute the camera shutter sound. But it opened a world of new possibilities to play with. Via F-Droid I downloaded the app “Kernel Adiutor”. A wonderfull app with loads of complex options. Since the FP2 is a fast machine, my initial goal was to lower the energy consumption to make the processor run cooler and the battery last longer. I changed some parameters in the CPU and Temp section and monitored what would happen.
By accident I started Open Camera - and the streaks where - gone!
To make it short.
It seemed, the streaks and lines appear if you operate the phone at a minimum CPU freq. lower than 1267 MHz. At a minimum of 1267MHz or higher they disappear.
Since this was not satisfying, initially I wanted to save energy 
, I changed the value back to 300 MHz and played with the governors - “performance” did the trick for me.
At least there is hope for a software fix.
I’m happy again!!!