In article .com,
"Jay Honeck" wrote:

Yesterday I found evidence of a larger leak than the ones we had
fixed in the main tank, which were obviously just seeps.

You didn't pressure test the tank when you had it out?

As you may recall, the first evidence of our leak (other than a faint
odor in the cabin when you first opened the door) was when Mary
spotted the rubber wing-root seal hanging down, fattened and gooey
from gas exposure.

Isn't "fattened and gooey" a symptom of using autofuel?

So, while I was under the plane cleaning out the central drain filter
(the 235 has a central "pee-drain" in the belly, like the Cherokee 6),
I carefully tracked down every stain. With the wing-root inspection
fairings removed, and a mirror, I was able to spot a tip-tank hose
fitting that showed evidence of leakage.
My A&P proceeded to dislocate both his wrists getting a couple of
wrenches on that fitting, and was rewarded with an easy 1/3 turn to
make it tight. He is of the opinion that this was our main culprit,
and that by tightening that fitting we have resolved the last of the
fuel issues.

The fitting tightness wasn't checked as part of the inspection process?
{Was this one of the items the owner was supposed to check? :-) }