My pressure gauge always shows a drop as soon as I start actually sparaying.
I always adjust the pressure by test spaying.
If it has been a long time, I test with water, set the pressure as I spary the water then run Laguer thinner thru everything.
When I am ready to spray the paint, I test spary and adjust the pressure if need be because the paint is thicker than the water, I will spray a few seconds to make sure the piant takes over and has washed out any left over thinner.
Now, if I could just quit jumping when the compressor kicks on and surprises me as I spray...LOL.
Practice practice practice.WATER, THINNER, then PAINT.