Worst Post-Production Pitfall: What's the Unfixable Mistake?

Hey everyone, Annika here. I'm currently cutting a corporate doc shot on an AMIRA, and we’ve run into a few snags that are making me pull my hair out. From noisy clothing to some unexpected RF interference, it feels like I'm constantly battling small issues. I've been experimenting with iZotope RX and trying various de-noise plugins, but sometimes it feels like a losing battle.

I was reviewing a general 'do not do' list for productions the other day, and it mentioned a ton of common pitfalls. It got me thinking: beyond the usual suspects that just take time to clean up, what’s the single most difficult mistake to fix in post-production, the one that truly causes the biggest downstream problems for an editor? What's your experience with that one nightmare scenario?