Commissioning challenges in robot/cobot cells — looking for integrator perspectives

Hello Everyone

I'm exploring better ways to diagnose behaviour in robot/cobot cells during commissioning and would really value hearing from integrators, control engineers, project managers, and commissioning leads.

A few questions I'm trying to understand from people who have worked on real deployments:

1. Which types of cells have you found to be the most difficult to commission? (e.g. welding, machine tending, palletizing, multi-robot cells, etc.)
2. When a commissioning project runs late, what are the most common causes? (Is it usually a mismatch between the design model and the physical installation, or something else?)
3. When something goes wrong in a new cell, how do teams figure out what physically happened? (What tools or data do you rely on? How long does that process typically take?)
4. How often do engineers need to return onsite after commissioning to troubleshoot issues?
5. If you could rewind and replay the spatial history of the cell — seeing exactly where robots, people, and objects moved over time — would that help diagnose problems?

Any brief examples, war stories or lessons learned would be incredibly helpful.

Thanks in advance!