US/LM 3

[Have at ye]

If it's some stalker-y jackass, and the security stuff seems to be borking out whenever he's having his "fun"... well, maybe he works for the security company? Or at least has the know-how on how to work around a basic security system, may give a clue as to who it is.

I would inform the authorities sooner rather than later to prevent any potential escalation, especially given that you are able to trust your local police department to do a proper job.

I'm glad you're not experiencing anxiety or panic about the whole affair. It's a good sign. Trying to scare you is probably what this person's all about.

EDIT

Maybe try setting up a nanny-cam or two without linking them up to anything else, place it somewhere without telling anyone, maybe this recording device won't stop working all of a sudden.

EDIT II

And the best way to catch a person sniffing around a place is old-school and non-tech: have someone watch the place whenever you're leaving it for extended periods of time. Perhaps employ a proper private investigation firm for this purpose (the local PD could have some contacts); they should also help with finding any potential surveillance devices or software.