Unable To Get Accurate Cuts Always 2mm smaller

I have in the past 2 Days updated all software.
Calibrated once before update 2 times after, tightend belts calibrated again twice as I was unhappy with first one.
Measured point to point on the calibration tool ( variance of maybe .5 - 1.2 mm depending on how you hold teh torch)
Cuts straight from the machine 150mm rectangle 147-148.5 depending on kerf value
Cuts from Fusion G code with post processor 150mm again 147-148.5
Some wild ones (managed 150mm and then ran the piece again and it was 147), of the hundred test pieces I have done, nothing works.
All cuts all test pieces done on a left hand outer cut. Tried many kerf values.
Varying points on the table, critical tests done on centre of the table, still to no avail.
I have no idea what to do from here.
PS Machine has not been bumped damaged or heavily used.
All measurements given are across X Axis but Y Axis was out previously but seems ok now.
I have just done another calibration and measurement use straight edge across X Axis and it reads 604mm on a 600mm straight edge.

I don’t know if this will help your situation, but left hand or counterclockwise direction is for inside cuts…Right hand or clockwise is for outside cuts. It is important due to the direction of air through the swirl ring. Right hand outside cuts on most plasma cutters are more accurate.

April fools day is next month