I have the -LED variant and mine also can be moved even when fully fastened down. I am thinking to put a piece of self-fusing silicone tape between the camera's "eyeball" and "eyelid" parts when I can be bothered to get up there and re-aim it.
Mine also has a slightly soft focus and a sort of double-exposure look to stuff, which I mentioned in this thread:
I'm wondering if focus can be improved on my cam, this seems sub-standard. I see the same effect at night on reflective license plates, definite "ghosting." It's a Dahua fixed-lens turret/eyeball. I would consider disassembling it if I could get a better result.
ipcamtalk.com
This is a second reason I am holding off getting any more of the fixed-lens variants. I'd pay $50 extra to get a varifocal (and focusable) turret. They obviously can do it, they just need to use the housing size from the 5231. I don't like the idea of a bullet where it's within arm's reach and offers easy grip and leverage to damage a $200 camera. C'mon Dahua, varifocal turret please