Check Valve on Arcan XL35 Floorjack?

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My many years old Arcan XL35 has always had a leakdown (with the handle correspondingly 'lifting' as it slowly goes down) issue since it was practically new. It's annoying. It works great otherwise. It's never had any leaks. I've tried the factory 'bleed' procedure a number of times over the years to no avail. The factory fill oil appears full and clean. Just the annoying leakdown problem...

Wondering about checking and possibly servicing the check valve that I'm guessing may be the culprit. Any ideas where it would be on this older Arcan XL35 jack? The 2 lower slotted plugs on the left/right (below), when removed, reveal recessed slotted adjusters - which I've NOT touched/changed. Would one of these 2 actually be where the ball bearings/check valve is?

Thanks,

PS - there is a feint outline (may not show below) of 2 small circles in the middle between the 2 adjustment covers - but scraping paint away theres only metal under - possible they 'plugged' this?

 

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Here's a slightly zoomed picture - still not able to identify a probable check valve that could be allowing it to leak down. There are two odd circles under the paint (scraped off)? Maybe it's somehow set up w/ a check valve inside the handle lock unlock shaft?