Jumping in on this thread late…crackers8199, my problem seems similar to yours. 2015 Model S, upgraded to MCU2 with SXM/AM/FM receiver. Since the upgrade, my SXM/AM/FM crackles anytime I turn volume up or down, and also at random/sporadically when listening to music. Now it also started cutting out for 1-2 seconds randomly when using Bluetooth for music or phone call, as well as when streaming. It is incredibly annoying and makes all audio virtually unusable. Took it to SC who told me it is a firmware issue, engineers are aware, and no ETA for the fix. Got a second opinion from another SC (I’m an hour from two different ones), same conclusion.
Two videos can be viewed at
https://www.youtube.com/@jarrodklunk, one on SXM and one on streaming. It is so bad that I’m thinking about getting rid of the vehicle. I have a mobile service scheduled for next week, but I’m expecting them to cancel it and tell me to wait for a (possible, but not probable) firmware update.