2013 Chevy Silverado 5.3; Low engine oil pressure

Okay so truck starts up fine, and runs fine for
about a half hour then the dash starts flashing
“low oil pressure stop engine now” and
beeping. This is the 1500 5.3l engine 70k
miles. It’s weird cuz the truck dosent have any
problems while it’s running. Purrs like a kitten.
Did some reading on the issue and followed
troubleshooting recommended by a mechanic
friend of mine.

We started by replacing the Oil pump
assembly (which is a pain to do in your
driveway without pulling the engine, or
dropping the oil pan). We started it up ran it
drove it about a mile and the truck ran even
smoother and then the same oil pressure drop
followed by flashing lights and beeping.

After this we replaced the oil pressure sending
unit, and the screen below it. Same issue. Ran
the code it was throwing and it said “oil
pressure sending unit performance” or
something like that. Sent it into a shop to have
them run a diagnostic and just have them
quickly change the oil and oil filter while it was
in there, and the best they could tell me was
that at 1000rpms it holds about 12psi and that
the code could mean the issue is somewhere
something on the interior of the engine is worn
out which seems odd to me on a truck with
less than 100k miles. Running it the oil
pressure seems to drop on idle, and rise on
acceleration until it just drops to zero and the
truck tells you to shut it off.

I’m truly at a loss for what to do at this point,
since registration is up, and I can’t pass
because of the code that keeps getting
thrown, and even if it did I can’t drive it
because the truck drops and tells me to shut
it off after the truck seems to warm up.