I have experienced the same thing with mine. I thoroughly cleaned every point of electrical contact (there was grease on the bare end of the battery tube and on the bare metal in the tailcap). I cleaned the both ends of the battery, and the contact plate where the positive end of the battery makes contact inside the battery tube and the spring in the tailcap. Then a little general fiddling with the battery and tightening the tailcap, I was able to get it to stay in turbo. It is definitely very finicky though. So clean, clean, clean and fiddle a bit you should be able to get it to stay in turbo. And of course you need a fully charged battery for it to stay in turbo for any appreciable length of time.