Dyllan,
First of all, welcome to Graybeards.
Do you live in a cold climate? Are you taking your uncapped loaded guns back inside the warm house at night? If you are, condensation forms in the barrels, and can actually wet your charge. When you shot your charge out and didn't hit the target, but then reloaded and did, this tells me either your charge has been comprimised or your rifle needs to be fouled before hunting. As was mentioned earlier, usually a rifle that likes to be fouled first will only print a couple inches away from a shot through a clean bore.
Just speculating here, but those rifles need to be kept near the same temperature once they have a charge in them. I either leave mine locked in the truck overnight, or in a locked cabinet in the unheated garage if not hunting that day. Pellets absorb moisture like a sponge, 777 pellets even more so, and they don't have that little bit of Black powder at one end to help out.
As mentioned, we need more information such as, rifle, powder, scope/sight, storage, etc.