Negative air chamber (The bottom one) leaking slowly pver time?
The imbalance of pressure (more psi in top than bottom) would create a setup like this
Having the pressures equal gives the best balance of suppleness but doesn’t dive under braking/steep stuff too much for me
Haing more psi in the negative preloads the positve so it goes into the travel a little, making it very supple on small stuff, but dives a lot under braking/on steep stuff/harsh bumps etc ..
If you playing with the pressures, make sure you set the top (positive) chamber first. The negative (bottom) chamber is a lot smaller so setting this first, then putting loads in the top cuases the pressure in the small negative one to ramp up far too much