Matrix MB-1000DN IR filter malfunction?

[videotiger 0]

I've purchased three Matrix MB-1000DN cameras over a period of the last couple of years to use for monitoring activity outside the front of our house as well as a remote webcam located several thousands of miles from here.

 

The MB-1000DN's are board-level cameras with mechanical auto-iris and mechanically-switched IR filters in the lense assembly. While the auto-iris function seems to be working okay, I suspect that the IR filter mechanism is malfunctioning.

 

On all three cameras, on at least one occasion, I've seen the camera go from being in-focus to going out of focus. On all three cameras, I had originally set the focal length and focus, then cinched the settings down by tightening the thumbscrews on the lense. On all three occurrances, the camera goes from in to out of focus over an event where the camera would switch the IR filter in and out (e.g. an overnight dark period). In one case, I refocused the camera, only to have it go out of focus (again) about a week later.

 

Clues indicate that the IR filter mechanism malfunctioning may be the culprit. I've never had any of my other cameras go out of focus like this.

 

Has anyone else had their mechanically-switched IR filter day/night camera do this? I'm now gun-shy of getting more of these types of camera after this episode--especially since one of these MB-1000DN's was located thousands of miles away when it succumbed to this malfunction . That camera was subsequently replaced with a camera sans an IR filter mechanism.