The load check on the lift/lower spool is designed to hold the loader from falling from the forces of gravity for a fraction of a second until pressure can build up. When the load check is not operating properly, you should see the jerking with the loader at any height but more pronounced the higher it is and the more weight in the bucket.
This is a typical symptom of a load check problem. The load check spring in the raise/lower spool might be defective or there is a piece of crud in the poppet and spring. Since it is a new valve, I vote for a piece of crud or some metal filings left over from manufacturing.
There will be a load check for each spool and they can be identified by a cap that closely resembles an unused port on the top of the valve. Carefully remove the load check cap for the lift/lower spool and remove the poppet and spring. Clean if required and replace. It's a 5 minute job.
