I've had this VHF problem for some time now with my Icom M400BB.
Problem is that on some channels reception got so bad that it was impossible to use (lot's of white noise over the modulated signal)
I did test it with other radios, and same problem.
After some testing on my boat I finally discovered that the router I used was causing this problem.
IE: As soon as I turned the router off, reception was okay again.
I als tested the router on a separate 12 volt battery, but same problem.
The router is used for a things like IP camera's, Raspberry pi (to monitor the solar panels and battery's) and so on.
Basically a LAN on the boat.
I did disable all the LAN devices one by one to see if they were causing the problem, but they are not.
Anyone here who can suggest a router without WiFi (wired only).
Preferably one that works on 12 volt?
It needs to have a minimum of 6 LAN ports.
Thank you for any information about this.