Hello all. I'm new here to LR ownership (but not new to cars, fixing, forums, etc).

Looking for some thoughts/leads on a knocking sound that recently started on my '19 TD6 with ~85k mi. Here's what I know and have done so far. Any thoughts appreciated.

- Knocking noise started about 1500 miles into a 2k mile airstream towing trip
- Did not seem to get worse after the last 500 miles of pulling the airstream
- Distinctly coming from left bottom side of engine bay. With hood open can't even really hear it with your head above the engine. Can hear it loudly near the ground.
- No lights or CEL
- Only happens when engine (and air temperature?) are very hot
- Kind of surprisingly hard to tell if it's engine RPM dependent. Tends to immediately go away right off idle, but not always. Can come/go if you switch from D to N to P or back again. Seems inconsistent on this, but it's made me wonder if it's transmission
- Blackstone oil analysis BEFORE the trip when knocking started showed extremely low bearing metal traces
- Have a fresh sample on the way to Blackstone
- GAPII isn't giving me an oil pressure reading (was looking for sign of bearing wear)
- Anything else I should check with GAPII?
- Does this motor have cylinder liners that are known to come loose?
- Could HPFP or belt tensioner make this noise?
- Anybody have knocking rod bearings that don't get quickly worse and/or cause other catastrophic engine failure?

Thanks!