CAT 930H Low fuel rail pressure

CAT ET is throwing a code for "low fuel rail pressure" (~2700 hrs on loader)

I have swapped the fuel pressure relief valve with a known good one from my second unit and problem continues.
I do not see any signs of leakage/ crushed lines and fuel filters have been replaced.
The lift pump is a mechanical type and I have replaced it.

Pressure is typically 6000-8000 psi until wide open throttle (WOT) and will go as high as 17900 psi under load

Historically when the problem occurred the...

CAT 930H Low fuel rail pressure

CAT 930H Low fuel rail pressure