Hey MichF,
Thank you for coming in and posting again to us, this is certainly a weird one as Kippies has mentioned!
I can see that you have been having some sound advice and smart questioning on what could be going on in the home. As mentioned, the TiVo remote has no inclination of time and this certainly sounds like interferrence from a IR perpective. I would like to ask do you have any sort of timed devices that go off during that evening, or maybe live close to any buildings of activity around this time, a shop maybe?
Keep in touch.
Ben