Yeah this has happened to me a few times actually. Did a session at a derelict mill in Derbyshire back in March and we got these really sharp bursts of static at around 3:10am, almost rhythmic like, then nothing. Recorder was a Zoom H1n so not cheap gear that would just pick up interference randomly.
The 3am thing keeps coming up doesn't it. I know some people write it off as the body clock or temperature drops affecting equipment but I've started logging the exact times of anomalies across my recordings and the clustering around that hour is hard to ignore.
Would be curious whether anyone's cross-referenced the static with other activity during the same session - like did your K2 spike at the same time, or did anything feel off in the room. Would help figure out if its equipment related or something else going on. Anyone else keeping records of this or is it just me being a bit obsessive about it lol