Canon EOS Rebel T6s always thinks battery is dying

My camera almost always believes that my battery is dying, even if freshly charged. I have several different batteries and no avail. It will still work to a degree, just always shuts down, which has resulted in my missing some good shots.

I believe that this is related to me getting it a little wet at one point, because the problem started then - also the lens no longer manual focuses, which is a lens-specific issue because other lenses are fine with the manual focus. I realize the water damage is likely the source of the problem with both of these issues, although separate, but wanted to know if there is a fix.

Got caught in a supreme rainstorm on a mountain without a protective bag, and despite my best efforts to shield the relatively new camera with by body and under shirt, some moisture got in I think.

Anyway, any advice or suggestions are welcome. Also note this model has no separate RTC battery that you can remove, so it isn’t that.