OK you either have a battery that can't hold a charge or some kind of parasitic load that's killing it. If you have the same battery that's seen a few complete disharges it may be toast. Is this a new battery?
Bike off, with a battery fully charged disconnect one side and put an amp meter in series where you disconnected it. You may need to move the red lead on your multi meter to the current jack depending on which model you have. Start with a higher range and work you're way down. There may be a low current and high current jack corresponding with your range selector.
If you start with the low current mA range and had a higher load you may pop the internal fuse in the multimeter and fool yourself thing there is no load since it's now an open curcuit and no current can flow.
Normal current with everything off is 2.5ma If it's more than that you have a bike issue, if not you have a battery issue.
If you're cleaning connectors get a platic safe contact cleaner.
Dielectric grease should be available in any autoparts place.
Sometimes called dielectric grease, dielectric tune up grease, or bulb grease. (clear silicone grease) The 3oz? tubes are a better value than the little .25oz squeeze packets.
It's normal for a battery to loose voltage at rest when you turn the bike off as it looses surface charge. Estimate of state of charge would be the voltage measured after the battery was disconnected for at least 4 hrs. 11.9 is pretty drained.
Bike off voltage of 12.1 is pretty low if it was fully charged when you turned it off.
14 and change would be normal when running.
:crackup