Can you try something for me?
Switch the return pump power off and allow the water to complete settle.
Open the valve on the intake/drain (left) up fully.
Restrict the valve on the return pump line (right) quite a lot, 80% or so (to make sure it doesn't overwhelm the drain). Power the return pump back on.
Watch and adjust the valve on the return (right) so the water line stays roughly a quarter to half way up the intake like this (keep the drain/left valve completely open):
Once it's roughly right, it should self adjust within reason.