Originally posted by johnyates
Insufficient voltage from the battery can also cause strange behaviour on some cameras.
Which might occur more frequently with an older, and therefor bit degraded battery, running almost low like <20%, hence weaker ; and in my experience (on K3) on heavy SDM (or sigma hsm) lenses drawing electrical power while focussing...
and add maybe also a non-pentax brand battery not fulfilling 100% the specifications.
In other words: if all the odds are against you(r battery), and electrical current peak demand is too high... voltage drops low and micro processor can be stopped.
Might also draw extra current: flash, in camera postprocessing like digital filter, high fps, bracketing, mirror lock, etc...
PS: never had issue with in camera focus motor, but already few times with my pentax 150-450mm lens on my older batteries.
If your battery is also from 2019... depending on your usage...charging cycles...
If you have multiple batteries, might need tracking which one.is suspect.