Might be worth fitting an oil pressure gauge in the cabin, I would prefer the mechanical type, but if you have a leak things can get messy!
Many years ago I ran a temporary mechanical oil pressure gauge via a plastic flow line in one of my tdi 300s to investigate some oil issues, easily done with a nice large clock for a few test drives.
Here we go for a bit of a confession.....
Once upon a time, I rebuilt a 2¹/⁴ diesel with a new crank and bearings supplied by the crank grinder.
All assembled and fitted back in the LR, time to fire up.
Sounds sweet
job done
Fortunately it had a mechanical oil pressure gauge in the dash.
Once warm, the pressure dropped through the floor and it didn't sound great
Long story short, I ripped the engine back out and buzzed gunned everything to death....... crank back in my hand running to finish in 90 minutes!
A quick measure and I jumped in the car. Slamming the crank on the shop counter I asked what size the journals were that they had ground?
Sheepishly and eventually, they admitted they'd supplied -10 and -10 when they'd ground the big ends -20 and mains -10