antenna
Seems unlikely in this case, but just this past weekend I helped out an RV12 builder with a very bad Comm static problem. It was intermittent. He had redone the headset jacks and thought it was fixed.... Long story short, I pulled the panel on the belly, left side, next to comm antenna. I disconnected the antenna cable and the BNC connector came off the cable in my hand. We then checked the cable coming out of the radio itself. Same thing. I put new BNC connectors on the cable and the problem appears to be fixed.
He (the builder) told me the cable had come from Van's. It was definitely not crimped properly, but it was crimped, just not properly. A very light "pull test" and the connector came right off.
As an aside, searching for the same problem last weekend, we discovered an error in the pin-out of the harness coming out of the fuse box. The result was that several of the fuses were in parallel. I felt this to be a serious problem, which we fixed. He reported to Van's and they said it was a known issue with the harness from some period of time and that it was still airworthy with the error. Personally, I disagree with that. There was essentially no protection on a wire that shorts since the current would be divided between the fuses, etc.
Simple test to see if this affects your airplane. Turn everything on including the radio. Then pull the comm fuse. If the radio stays on, you have one of these bad harnesses.
Coincidentally, the radio static cleared when we corrected this so I thought maybe it had just been a weird RF grounding path issue. What really happened was that our monkeying with the fuse panel, we shook things enough so that the bad antenna connectors made proper contact temporarily.
Sorry for the long note. Just thought on the off chance you were fighting the same root issue, this might help.
-Joe