I have the same issue with the same competition air rifle. Not sure if the seals are just dried out or if they need to be replaced. I did apply some pellgun oil two days ago and have made a point to shoot 20-30 rounds through it the last couple days and that seems to have helped but it's still losing air over night...20-30% I'm hoping that shooting it will help the lubrication to eventually migrate to the seals and possibly rejuvenate them but it's too early to tell. I also have a email into Crosman as well. BTW I've stored mine fully charged overnight for a couple years and never had a leak so I don't think it's a design issue but more a non use issue...they do need to be used now and then.