A couple of times ago my wakeplate was acting up...sometimes working, sometimes not. Then it worked the next time out....but now it's 'dead'. I still hear the low-pitched 'humming' noise when I tell it to go up/down, but the plate doesn't move. Doing a search here I couldn't find any other examples of this problem...and no items in the manual to help me out either. Is it something as simple as filling up hydraulic fluid?