Yeah this has happened to me a few times out on investigations in Cumbria. I use a Zoom H1n and there's been nights where I get this weird crackling burst right around that time, nothing before, nothing after. Checked the batteries, checked the environment, no obvious explanation.
Not sure I buy into the "3am as witching hour" stuff fully but it's hard to ignore when the timing lines up repeatedly. Could be temperature drops affecting the hardware I suppose, that time of night things get proper cold up here.
Anyone keeping a log of the exact times? Would be interesting to see if theres a pattern across different locations or just a coincidence thing. I've only got maybe 4 or 5 instances but they stand out.