07 F-50 tilt and trim issue?

My 2007 F-50 tilt unit seems to be losing pressure somehow. When parked in the garage, I leave the motor straight up and down so it will fit. I have noticed that over a period of two days or so, the motor slowly begins to drop to a lower trim position. There is no oil on the floor that would indicate a leak, is there a problem with air in the system or something. It is under warranty, just thought I would check here first.

[boats.net]

There should be a 3 year warranty on it. Check to see if manual release screw on side of transom bracket is tight.

I actually got the 6 year warranty with this motor (helped make my decision on Yamaha)...I will check the screw...Thanks