What did you mess up on your renters insurance claim?

I've been researching renters insurance claims, particularly theft claims, and I'm noticing a pattern: a lot of people end up with denied claims or partial payouts because they missed procedural steps or failed to document properly upfront.

For those who've filed claims: what went wrong? What would you do differently if you could go back? And what part of the process surprised you?

I'm trying to identify where claimants typically stumble so I can better understand the gaps.