The way I see it, you have three choices:
1) Say nothing about his behavior, and keep inviting him while knowing full well that he is likely to back out with a lame excuse.
2) Address his behavior, and expect him to make a lame excuse as to why he behaves the way he behaves.
3) Stop inviting him, thus avoiding his inevitably lame excuse.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.