I have a third idea, the pump could be knackered. Because if you have weak hydraulics and jerky lift arms, you could have where your pump just can't build up enough pressure to lift the arms when you have something on or the jerk if it suddenly lifts. But in theory it could be a bit of all 3 suggestions so hard, you have. It could be low in oil, a knackered pump and oil leaking out of the cylinder under the lift cover.
Check your oil level first, then put something heavy on the lift arms, raise the arms near the last, and turn off the engine to see what happens. If the seals are bad in the cylinder, the arms will drop like a stone when you stop the engine. If it stays up and only goes down over night, they're not too bad. If you put on something heavy and it struggles to lift all the way to the top, I be thinking your pump is shagged