Before changing the oil, take a good look for leaks, especially around the rams. If there are leaks, the fix is doable but can get complicated if the end caps don't want to unscrew.
If you see no leaks, I agree it is probably a bad check valve and changing the oil may help. It is worth a try. Note that bleeding is necessary after a refill and for your safety, don't stand under the motor when tilted up, use the stops, keep your fingers away from all moving parts and read up on the steps to change the oil.
If the motors seem to tilt up differently, for example one stutters or goes up slower, you may have air in the system usually due to low oil. Filling and bleeding will help.
Good luck.