PRO-531 Dome - Blurry at night due to IR insolator improperly sealing camera
The problem that you are describing is in fact quite easy to resolve. It sounds like the foam ring isolator on the lens isn’t making contact with the protecting glasss.
What you need to do to fix this is simply open the camera. Pluck outward the foam slightly . Then close it back. When you close it back, the glass should touch the foam isolating ring.
Once sealed correctly, IR light will not bounce back into the lens.