I’ve seen this here mentioned a couple of times but now I saw for my self with the FP6: ghost touches and swipes (even deleteing a couple of messages in the process 
).
It made it impossible to switch off or reboot the phone with normal means.
eventually I was lucky
What would be the best course of action to be liberated from this?
Just to double check: is the screen entirely clean and free of water? Raindrops can definitely cause some ghost touches.
Thanks! yeah I checked that. No water no dirt. I did put it down on the table when it happened so nobody and no thing was touching it. Rather ghostly tbh.
Problem started when it random started switching flight mode and selecting and deleting messages. And that there was no way to switch it off (long press the on button like on the FP3 doesn´t work any more on the FP6)
My deepest sympathy: FP4 had an epidemic of this some years ago, there is still a thread about it somewhere in the bowels of the forum. If you have time to waste, read through it. Nobody found a solution.
Fairphone eventually tried to fix it by simply reducing the screen’s touch sensibility, which in turn caused phones which hadn’t that problem to be hard to use because they didn’t register your finger anymore… 
If that continues, that’s imho a warranty hardware case for support.
Today I had a similar experience on my device, I had to press the lock button to stop the ghost touches. After it I turned off the Touch Sensitivity in the Settings. I don’t know if it was the reason, but I give it a try to this. The screen was clean, no raindrops etc.
This also started happening to me a few weeks ago. I’ve been using my FP6 for 6 months without seeing the issue even once, and out of the blue it just appeared.
It’s only slightly annoying - I only get a single ghost touch immediately after unlocking the phone about 30% of the time. It seems it’s not connected to any update, since it started happening about 2-3 weeks after I installed the December update.