Take it of the bike, turn it to its lowest setting (Öhlins) then pump it a few times. Then turn it to its hardest setting and pump it again. You’ll feel the difference. Squishing noises are normal. Interruptions in the feel mean rebuild time. One other test. Softest setting, middle of stroke. Leave the damper sit for a minute or two. If the very first part of the movement is hard then gets back to normal then it’s time for a rebuild. This is a common Öhlins failure. This type of failure, with the damper on the bike, feels for all the world like notched steering bearings.
With the Saches damper (none adjustable base models) just cycle it a few times and feel for anomaly’s in the stroke.