I've got a 1760 12 row wing fold planter. When folded out in planting mode, I can raise it all the way up & as long as I have the handle pulled back on my 7810, all the cylinders are fully extended. When I let off the handle, only the outer cylinders relax an inch or two. Also when I'm planting, it seems to hump in the middle a little but all wheels have slack in the mounting pins so no pressure is one them. I didn't notice this until I was planting again yesterday. I took the handle off the main valve body and took the balls, springs and plungers out and cleaned them and put it back together but it did not make any difference. Any ideas what I need to check?

TIA