Oh, got you. I understand now. I was thinking you meant something back in the lines.
So, would THIS be the problem? (See attachment)
The fresh water tank used to fill up slowly while hooked up to city water. I kept running the tank empty with the electric pump to clear out crud from the check valve.
Would something like this maybe have been my issue there, as well?
I ran it last week again, and it seems to have cleared out the bypass leak, and now immediately afterward, this chunk of crud appears just a few feet from that pump.