Yes PCM can help. The trouble is you never know if it will help enough. If it don't then you have a real problem. its better to eliminate the problem if you can. Then use PCM.
The problem with flying wires is not shielding or reflections or multipath usually. They can be a problem but very unlikely.
The problem is vibration on the wires cause buildup of static electricity on the wires. This is the same thing as rubbing your shoes on a carpet. This causes a difference in potential between the wire and other metal parts. If this wire and the other metal parts are in intermittent contact there will be sparking at the contact area. You will not see it but your receiver can hear it.
The cure is to isolate the parts with plastic connectors, or bond the wire securely to the other metal part, or use non conductive flying wires.
This problem can come and go depending on the humidity.