Tom, as you know, I am of the same view as Flashy Mike on this, the root cause of the Q8 shutting down when a bump of sufficient magnitude momentarily disconnects the cells is because the MCU very soon loses all power (possibly even in as little as a few 10s of microseconds, but my analysis took no account of the other capacitor in the circuit, the voltage level at which the main LEDS stop drawing current, etc. etc.), then re-boots, leaving the torch turned off.
I did a very rough analysis at Q8 modding - #678 by Tom_Tom
I have enquired behind the scenes for more accurate information about the MCU current drain, to improve the analysis, but to-date none has been forthcoming.
I think that Flashy Mikes addition of e.g. 100 uF holdup to the MCU is the correct engineering solution, and something that could easily be done by someone wishing to eliminate this problem.
I also recognise that strengthening the springs will also improve, but possibly not completely eliminate it.
In the Q8, as supplied, it appears to be consistently reproducible. Improving or eliminating it, for those who consider it to be of concern, e.g. those who rely on their torches in outdoor use, requires modification, either to springs, or electronics.
For many, perhaps most, it will not be a concern. For those of us for whom it very much does matter, modification can fix it, and the modding thread is the best place to discuss that.
I should mention that this is not a unique issue, I have other SRKs which do exactly the same thing, it is a consequence of the cells having springs only at one end, as in many other torch designs. The positive connection requires solid contact between solid metal surfaces, so will inevitably be interrupted by a sufficient shock at the tail, as with any other torch with only one spring. Ensuring the electronics carry on operating through this, is best addressed in the circuit design.
I would please suggest that further discussion of it be carried on in the modding thread.
Consider it a “feature” of the Q8 in unmodified condition.