[JohnStrangeII]

That's how I use the word, too. It's a Heisenbug, though only one that manifests itself when you try to present something.

[lispm]

A Heisenbug can be observed in many situations. The Vorführeffekt happens only in front of an audience.

[beerandt]

I think I get what you're trying to say, but by definition an observation requires an audience, even if it's an audience of 1. Maybe say an increased audience size?

[justnotworthit]

I think a "presenter" is required.