Yeah last night was the first time I experienced "auto shut off" with the MS "mystery switch tail light. I thought it did not make any difference how much rotation you gave the light to affect an "on of off" setting but apparently - you can indeed turn it "barely on" and have it go off without warning.

Like I said though, first time it happened in 40 or more operations.

Of some note -if you examine the beam of a MS tail light you'll be amazed to find a "sliver of intense light" at as much 150 degrees off-axis. I've never seen this is any other light - of any brand.