What made you stop trusting a demo?

Genuinely curious, because I am on the making side of this and I want to know what we are getting wrong.

We build real-time face and voice models, so demos are most of how anyone judges us. The tell I have become allergic to in our own material is the cut. If a video edits right at the moment the product would have had to respond, the edit is doing the work the product could not. Anyone who has built something real-time spots it immediately, because you know exactly what got removed.

The other one is a demo where nothing goes wrong. Real usage has friction, so a flawless run starts to read as rehearsed rather than good.

So what is yours? The moment in a demo where you quietly stopped believing it.

Interested in any category, not only AI. If you evaluate hardware, or dev tools, or anything that arrives with a sales engineer attached, I would like to know what the tell is in your world.