Whats the antipode to this, where, as a programmer going to investigate a user bug, my mere presences makes the bug disappear, and the user frustrated at trying to reproduce it for me?

Because this happens a lot to me these days, no kidding. The bug happens, some user delights in calling me over, I take a look, they simply can't reproduce it, I walk away - they get the bug again - and, yeah, I kind of have to race ahead of things to understand the nature of the users situation.

Happen to anyone else? I don't think its quite like Vorführeffekt, and is maybe a bit more like Daseinsvermögung oder etwas ..