Seems like I'm going flashlight buying crazy here. I ordered an Olight T20 as a Chritmas gift and it just came. I can change from SOS to strobe to normal illumination with the tail switch but I can't change it to the 5 different brightness levels. The instructions say to turn the head 1/8 of a turn clockwise and then 1/8 turn back counterclockwise - but it doesn't change anything. Any suggestions? Thanks.