A couple of things-
If you use a DMM to charge your batteries, keep in mind the voltage limit of nearly all 18650 cells is 4.20 volts. Anything over that begins damage to the cell, heat, pressure and eventually... rupturing.
Acetone will clean your lens (do not use acetone on plastic lenses) or 99% isopropyl. 91% seems to work OK as well. Use a clean q-tip and touch lightly. Make a circle from the outside perimeter of the lens and spiral inwards towards the center in one direction only (clockwise or counterclockwise) and avoid overlapping. If it's still not clean, use another clean q-tip and do it again. If it looks the same as it did after the first cleaning, the backside of your lens is dirty. If it still looks the same after cleaning the backside, your diode window (if you have one) is dirty. Use the same technique but be ever gentler on the diode window. If it still looks the same your lens or diode is damaged.