Beyond 'On-the-Nose': The Ultimate Amateur Script Red Flag?

Hey everyone,

I'm Marcus Johnson, a working writer/director trying to hone my craft further, and I've been wrestling with a particular question. We all know the common advice to avoid 'on-the-nose' dialogue, and I've been actively scrutinizing my own scripts to cut out anything that feels too blunt or expository. It's a constant process of refining and digging deeper for subtext.

But it got me thinking: if 'on-the-nose' dialogue is a frequent culprit, what's the most revealing mistake, in your experience, that immediately screams 'amateur script' to an industry reader? Is it something even more fundamental than dialogue, or a particular type of dialogue slip?

I'm talking about that one thing that instantly makes someone put a script down. What's the biggest 'no-go' you've encountered?

Thanks for your insights.