Water pressure mystery

I am trying to trouble shoot my paramount in-floor cleaning system - it’s simply not doing it’s job.  Jets only halfway pop-up, and the pressure guage on the manifold is reading between 6-8 PSI when manual calls for between 20-25.  So it’s clearly not getting enough pressure to do what it’s supposed to.  This pool was installed by a previous owner, and they must have really annoyed the builder because they won’t give me any support, but I have to at least give them the benefit of the doubt that it worked when they installed it.

Anyhow, upstream of the manifold is all Jandy equipment - salt cell, check-valve, cartridge filter, heater, pump and Jandy valve.  The pressure guage on the filter housing reads 32 PSI, and I’ve purged any air when it is present (i.e. after I vacuum since the floor cleaner doesn’t do it’s job!).  There are no air bubbles coming from the floor jets, and I have not been losing any water.

The only thing I’m not sure of, the bubble/window over the pump basket shows the basket only about 80% filled with water when running.  I have checked everything I can find with the exception of taking the heater apart to see if it’s somehow got an obstruction.  Any thoughts on what else I should check will be greatly appreciated!

-Pete