JLG25AM Manlift problem

I have a JLG25AM manlift it is about 10 years old and in very good condition....It is rarely used and stored inside a heated building...There is a new deep cycle battery.......I got the manlift about 2 years ago...I used it a year in light use and now it will not operate at times... There is a new deep cycle battery that I charge every week or so ......The battery has been tested by myself and the dealer and it is perfect... When I press the 2 buttons to go up it will go up at times and sometimes not...Sometimes it will go up and when I stop pushing on the buttons i try to go up again and it won't go up...You can hear the motor trying to make it go but it won't..It always goes down ok....This mysterious problem will occur most times now....It acts like the battery has no charge but i may have just charged the battery a few hours earlier and it still won't go up......All the lights on the outriggers are on so that indicates good connection to operate... Can anyone give me advice please ? Thank you very much..........