Start with whoever accepted the finished brackets. They may have a separate inspection sheet. I helped assemble a handover where the production tick only meant the part was ready for the next operation, which nobody had written beside the tick.
Then ask the fabricator how they decided a bracket needed straightening. There might be a gauge or a comparison sample that never made it into the folder. I would want that explained to the fixture designer.
Toby, you can still use the final sheet to describe what was accepted. Just do not ask it to explain the earlier condition. The missing readings will need new evidence if they matter to the fixture proposal.