Ah,
@Dan here has pointed out my error, sorry.
I grabbed a Hikvision flat-dome that was laying around in the office for the last photo that I uploaded. He has pointed-out to me that the latest flat domes e.g.
2555/
2563 now use IR LEDs that are no longer within the camera/lens dome bubble.
They have x2 small IR LEDs placed external to the dome bubble, one either side.
The camera cover has diffuser covers for these LEDs.
Whilst this design change probably solves the potential for internal reflection issues, we are concerned that in use-cases such as yours (where you are mounting the camera horizontally under your soffit and wanting all the IR light to project forwards from the building to the scene) it is likely to render the IR LEDs fairly ineffective i.e. the proportion of IR light going to the scene from your mounting position / orientation is likely to be very small. And, in fact, a great deal of the IR IS going to be bouncing back from the wall and other surrounding surfaces - resulting in the poor images you have seen at night.
Unless you are able to mount the camera to the wall or front of the soffit/fascia (and present the infra-red LEDs pointing forwards to the scene), I don't think that camera model is now going to be suitable for your application and mounting position.
I am sorry, this is a product change development, and yours is the first application where the resulting problems have been presented to us.
I think the two IR LEDs now need to face forwards, to the scene, and effectively the lens needs to be looking through pretty much the crown of the dome bubble.
Sorry, if the camera is therefore not suitable we'd be happy to take it back and refund you.
BTW -
@Dan is also running tests with this camera model now in regards to audio capture and playback.