3 pt Disc Mower Hydraulic Lift

I use a New Idea 5407. After mowing for a couple of hours when raised to lift the bar does not fully lift.

It only has one hydraulic line. I bled off the cylinder by opening the top line fitting and hydraulic oil came out. Bar lifted to normal transport position. I lift the cutter bar when I make my corners. After mowing I have to continually bleed the cylinder.

I am thinking that the seals are bypassing.

Would 2 hydraulic lines help but take away the float?

Possibly just a low grade cylinder?

Thanks,

3 pt Disc Mower Hydraulic Lift