I assume what you are referring to is the fine focus adjustment at the eyepiece portion of thescope keeps coming loose? Why it continues to loosen I have no idea, could be way of carrying it, etc. However whether the scope is the reason for the misses???? It appears by your post that it was fine at your last range session but have nottested since. Sorry,until you do a follow up session we can't give you any real help

.
Buying a new scope at this pointwould be as uesfulas blaming your current one! You need to widdle downthe possibilities. Get to the range and shoot. Please don't go hunting until you do. Owe it to yourself and the game!
BTW expensive scopes fail too.My buddies 1 year old VXIII packed it on him. It happens, though at this point it is just an assumption (made easier by the "cheap" label given).
Good Luck