22 psi is too high for a cartridge filter. I think that misconfigured valves are the likely cause. The filter might also be dirty. I suspect that insufficient flow is causing the cycling.
The suction manifold is all of the "T"s connected together to combine the flow from all of the suction lines into one going into the pump.
The pressure manifold is where the outflow from the filter branches into individual lines going back to the pool or spa.
I would say that the next steps would be to clean the filter and figure out the plumbing.
I think that the suction might just be pulling from the pool main drain.
Can you verify good suction from the spa and good return to the spa?
What pump do you have?
The suction manifold is all of the "T"s connected together to combine the flow from all of the suction lines into one going into the pump.
The pressure manifold is where the outflow from the filter branches into individual lines going back to the pool or spa.
I would say that the next steps would be to clean the filter and figure out the plumbing.
I think that the suction might just be pulling from the pool main drain.
Can you verify good suction from the spa and good return to the spa?
What pump do you have?