So if you think there is a mundane explanation... shouldn't you be able to present it? Surely in those cases with mundane explanations this would be easy. And don't conflate what I'm saying with cases with insufficient information from which no conclusions can be drawn - I'm talking about those important cases where sufficient information is provided and the sighting as described cannot plausibly be of anything mundane or explained psychologically.
Unfortunately, no such cases has been presented in this thread and furthermore, as you have mentioned yourself, one can't prove a negative. You can never be sure about when you have examined all mundane explanations.