So until earlier today, my vamo v5 worked fine with either battery types. I heard it clank against my door as I got into my car and it stopped working with the 18650 I had inside it. I thought maybe the battery was drained. I got home and put another 18650 into it and that one didn't work either. But it does still work with my 18350. Anybody have any idea why this would be? All batteries are flatops.