Pure conjecture here but it wouldn’t surprise me if that spike is actually a defrost cycle on a fridge/freezer (which invariably happens once every 12/24 hours) whereas the nice Device waveform that Sense presented you with was a phantom triggering of an actual load. Meaning: some other device signature or power pattern looks like the defrost cycle to Sense.
That said, an actual defrost cycle (if not malfunctioning or triggered repeatedly by a wonky thermostat) usually runs for 10+ minutes to defrost so these short actual spikes (in the mains PM) are not looking like that.
My suggestion would be to ignore things for a week or three and see what is happening then. Feels like Sense is getting familiar to things and in the “confused” stage.