It would help if you put some kind of foam pad inside the light to prevent battery bounce when you're switching as that throws off the logic. I used the supplied foam washer, cut to half thickness, and dropped into the tail without use of the glue (don't peel off cover). Other people have used Dr. Scholls foam washers successfully.
If you have that, then a very short turn off/on cycle (2 seconds off is too long, 1 second off may be too long) should get the light to switch modes.
Worked for me...
