hello nixie,
I found that problem also,
here a P20pro,
I bought a charging adaptor for the car, never any problem.
Then I bought a 1 meter usb cable while the original charging cabe is very short.
When charging the handy with the 1m cable, the radio was worst case ! With the short cable, nothing, all best.
So my tip is to swap the charging cable and test again.
Martin