Hydro's are jerking on Lesco Stand On mower

I bought this mower used awhile ago, the hydro's aren't smooth to react when they're engaged. I've changed the fluid and filter and it's the same.

The mower only has about 280 hours on it, I've never owned a unit with hydro issues; they aren't making any growling noises that would indicate the normal issues I've seen.

Should I try to purge the system? Any recommendations would really be appreciated.

Thanks