Okay, sounds like a different point to check??
The drawing is not the best on the years before 2010 but this seems to show there is a vacuum breaker fitting above the wet bay that might be a problem if I understand where you mean when you mention above the F.
These are gizmos that I have not had trouble with but also never liked the idea too much either. I do work with lots of water that has lots of minerals (hard water) that leave gritty deposits on everything they touch.
The way I understand these vacuum breakers to work is that they are designed to let air flow in as a way to make sure the pipe drains to avoid freezing but then they are also supposed to close when you are running water and that is the point where I wonder!
IF this is near the point you feel is leaking, take a look at this drawing and check if you see what I'm looking at on the design. Does it look like they show a small pan to catch any leaks----kind of like they thought it might be a problem?????
Maybe the little pan caught small drips for years but now it just overflows and runs down the pipe to the wet bay?
No help there on how to access it, though!