Old IPC-HDW4631C-A - High pitched beeping noise with some pattern, cameras not operational

[troglegranular]

I've got some old Dahua IPC-HDW4631C-A 's, and 3 of them stopped working within about a week or so's time. They are originally gray market cameras, and are a good 5 or so years old at this point. Up until failure (some months back at this point), they've worked as well as expected. The odd part is that 3 of them stopped functioning at around the same time. They're all indoor cameras, and I can't make any sense as to why these 3 in particular stopped while others remained functional. It's not a cable fault, not a switch fault, and not my NVR's fault. The IP cams themselves don't seem to be operating properly, as they don't have an IP address (that I can find), their IR modes aren't functioning, and finally the cameras themselves make a very quiet and moderately high pitched tone.

It's that last part which gets me - these aren't speaker equipped as far as I'm aware. My intuition says that it's either a debug speaker as you'd find on old computer motherboards (basically just a basic buzzer for debugs), but perhaps it could be something relating to the IR filter's motor? I can't really find anything about this with a quick search and I've never stumbled across this before. I figured I'd ask somewhere before taking any additional steps.

I was planning on replacing these cameras, but before I go through the trouble of that and changing out the mounting points for the camera housing, I wanted to rule out the possibility of reviving these cameras somehow - if maybe the noises I'm hearing meant something to someone.

Thanks for your time and help!