Just took in the "Princess's" 05. The 3/8" fuel line, above the rear axle, in the plastic retainer attached to the floor pan had a pin hole leak.
No rust on the line, retainer is plastic, no rocks or sand wedged under the line, and line seems to have no torque stress.
Check your fuel lines at that retainer next time you're underneath.
I have a 03 Ram 2500 Cummins truck and every now and then the, "Princess", will let me peel around in her cute little ratt'ler. What a wonderful
fun 4x4 to drive........

Did any drivability problems lead you to look underneath the Jeep? I ask because I have been having problems that, to any old school diesel mechanic, would lead to some air in the lines. Of course there are no codes stored and the CEL isn't on so the dealer says nothing is wrong. Symptoms are: When starting after it has been sitting a few days, it will shake and cut out. Also after a high power run, it runs rough and shakes for a about 20 seconds, like a gas engine that has a slight misfire. I noticed the connection in back that you mentioned. Mine are clean and dry. The hoses into the fuel filter however have a slight oily coating around the clamps.

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2006 Liberty CRD-SOLD
Dynomax 2.5 exhaust

No CEL's, ran good, could always smell diesel. Noticed spots on the garage floor and bingo the "Princess" saw the drip.
No line set in the whole 5 state area (ND, SD, MN, WI, IA). On order from Deeeeeeetroit, Motor City, comin' from the Maaaaaaaaain office.
These Lil' Ratt'lers are unique.
The 3/8" line is no pressure, so drip drip drip she goes until Dr. Z gets us the line set.
When's the last time you changed the fuel filter ?
Contaminated fuel ?
Do you use a fuel additive ?
Fuel cap ?
Air filter ?
Sometimes its something quite simple on these beasts....
Then again...
If I hear of a sure fire cure I'll certainly post it. We're ALL in this together.