Well ..... the winner is Ed & Bill. I got to the point in the "do-over" where it was time to punch down one of the two troublesome keysets. Did so, and the noise came back. Opened up the keyset, and someone had already snipped VIO/BRO and put a scotchlock on it. Also YEL/GRN - GRN/YEL were disconnected and just hanging there uninsulated.

I hate opening a keyset and finding a scotchlok.

I disconnected the pairs and the noise is clear.

Anyway, if anyone has the time, can you explain why the last 3 violet pairs cause these issues if they are teminated at the block, but not the keyset? Does it cause some sort of induction or something?

Thanks
Matt