Here's something I've learned:
I was using the CFC hose to fill my GF and Sparge Heater as it provided a nice hose for me to fill everything. I then started getting a really nasty plastic/vinyl flavor in all of my beers, deposit 12-15 successful brews with the GF, using campden on all just to be safe.
So last week I go to brew again (I took a break from brewing because I'm basically going to have to dump 4-5 more kegs, and I've already dumped 3, which is both painful and disheartening), and I use bottled water because I know our local water is hard and gets worse in the summer. At the end, when I hook up my CFC to get ready to cool, the water being discharged from the fresh side of the CFC smells HORRIBLY of plastic/vinyl. It was at this moment that I realized the problem was my water supply, per se, it was that sediment had collected over the 15 good brews in the CFC. I always pump pbw through the fpart of the CFC that the wort flows through, but that didn't help the fresh water part that never gets cleaned.
I supposed I could hook up a pump to clean the fresh water part of the CFC, but in reality I just will not use the CFC as a fresh water supply hose going forward. I don't think your issues are related to mine, but I wanted to throw my experience out there.
Another thing, I always dump the first pint or so of wort down the drain before I start running the boiling worth through the CFC to sterilize. In my mind, this gets any residual water that may be left from the last brew into the sink instead of my wort. This is hopefully just being overly cautious.