I noticed a degraded response of the touch screen while charging, too. It was when drawing a pattern to unlock the phone, I had to make a second, more careful attempt. Not really a problem for me, I charge the phone mostly when I’m not using it. No problems outside of charging.
Not using a screen protector.
I suspect that there’s not much one can do (greasier finger …?) and any software patch might well throw something else out of kilter…
@Tobi_Kuik Your case sounds a bit different and might be a problem with your unit or screen. It might be worth taking it up with official FP support, though that might mean all the hassle of sending the phone back.