Lots of threads around here about that. The common cause is low quality valves letting that leak down happen. If you disconnect the QDs & it still leaks down while not attached to the valve it's obviously a cylinder issue.
Many people prefer those pilot valve cylinders. You need to apply significant hydraulic to the outside of the pilot valve for them to pop open. So they only let the cylinder move when you hit the lever. The drawback is a float valve won't let them float. I find float useful enough a piloted valve has never been an option for me. I also got good valves & cylinders from FitRite for that took a week to leak down on my
L3200. Have OEM Kubota float valves on my new
L4060, but yet to get the cylinders ordered with the tractor back before Thanksgiving. So I can't say anything about the OEM Kubota solution yet.