Oil pressure - weird!!!

[hairyhoover]

Hi, ive got a very very stange oil pressure problem, ive changed oil and filter but with no change is results.
 
Ive got 2 gauges my oem gauge(stock locatoin) and my SPA temp / pressure oil gauge(under oil filter) .The gauge/sensor is new and tested.
 
When the engine is cold i get lower pressures when hot at certain RPM which is all wrong.see below.
 
1000rpm
cold = 30psi
hot = 20psi
 
2500rpm
cold=35psi
hot=50psi
 
3000rpm
cold=40psi
hot=60psi
 
4000rpm +
cold=n/a
hot=35 psi
 
I have taken a quick video have a quick look. I really dont get it!!