PVS-14 auto-shutoffs are unreliable at best, and an example of the "good idea fairy" at work when it was spec'ed out for the device, and many professional users that have a good bit of experience behind PVS-14s actively disable the function, and I know of almost no one who knows what they're doing that actually relies on it even if they don't actively disable it.

The easiest and most reversible way to disable it is simply to take two small pieces of electrical tape and cover the contacts on either side of the threaded hole for the J-Arm.

To answer your question directly, what you're experiencing with it cutting off at "non-standard" angles is by no means unusual.

~Augee