disc brakes and oil pressure

1) I'd change the oil sender unit for the dummy light. Maybe its tripping at too high pressure? Did you check the gauge pressure, with the light on? assuming you have a guage and the dummy light. correlate the "light" with the guage.

2) You may have a split (crack) in the pu tube maybe near the top or midpoint of the tube. If not a crack, maybe the PU tube is loose at the oil pump. Was it sealed properly? IN that case, change the PU tube.