Originally Posted by Juha

@ OP: This particular moron has endorsed L2D with reservations, so take this with a grain of salt. My L2D acted exactly the way you describe when I used it with old rechargeable NiMHs. In my case, occasionally switching modes turned out to be caused by weak cells too. Not bumps (which is what I suspected at first).

Now I carry a spare set of slow-self-discharge rechargeable AAs - I can keep them in the bag for weeks without noticable difference in performance. They have less capacity but will get me back home when (not if) the light runs out of juice.

You have two lights, so it's unlikely they're both faulty. You seem to be sure it's not the cells, so maybe the P2D is indeed inferior light. I haven't used it myself, so don't know. I do know not all Fenix lights are like that.
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@ everyone: I edited a couple of posts. Please keep the discussion within the Guidelines from now on. If in doubt, read specifically the part regarding vulgarity. Thank you.

--Juha, a Forum Mod