Five observability gaps we keep seeing in production voice AI stacks

# Been building and running voice agents in production for a while now and wanted to write up the failure modes that keep showing up across stacks. Posting here because I'd genuinely like to hear what others are seeing. The five we keep hitting: 1. Teams blend infrastructure failures and conversation failures into one quality score. A VAD misconfig is not a conversation problem, but if your dashboard treats them the same, you debug in the wrong direction every time. 2. No visibility into VAD performance. When this layer fails silently, the agent looks dumb but the actual problem is two layers upstream of the LLM. 3. Sampling at 1-2%. Statistically guaranteed to miss accent-triggered misclassifications, late-call breakdowns, and underperforming segments. The stuff that matters lives in the long tail. 4. Auto-generated evals from failed calls. Produces noise that looks like signal. We ended up building a human-in-the-loop annotation flow at the sentence level instead. 5. Evaluating at the agent level instead of the campaign level. An agent can score well on average while quietly tanking a specific campaign objective. "Does this agent speak well" is the wrong unit of evaluation. "Does this agent serve this campaign goal" is the right one. Curious what others are running into. What's the failure mode you wish you'd caught earlier?