Well my suspicions have been confirmed 4.8 bar is not enough to get the front to a normal ride height. from 8-9 bar the car should be at a normal ride height and your compressor is at least capable of that, but the charging of your front axle cant get above 4.8 bar which points towards a leak.
I made a video of going through the various steps of discharging and charging the accumulator and front axle proving how a working system should perform, as I state in the video the Basic setting portion of the video will look different to your setup as I have made my own label file to make it easier to do but the results are the same and you can see which block numbers are being used to perform the tests in the video.
https://youtu.be/OU5SBmHQIfI