Loosened focus ring, now stuck focusing <4in

[HDRock]

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Foggy image - possible hardware solution

I recently realized that some of my wyzecam 2s had a very foggy image compared to others. I took one apart to get to the bottom of this and to my surprise, I found a very scuzzy little piece of glass under the lens of the camera but over the sensor. I cleaned it off and the difference has been pretty drastic. I’ll try to fix another camera and get some before and after photos. Can anyone explain the purpose of this little piece of glass? UV filter? And do you mess anything up by cleaning it…