Record which revision of a proof was sent to the reviewer.
Email the current proof to its reviewer and record the version sent.
Your reviewer gets the current image or PDF and a clear question. Your review card shows which revision you sent.
Keep the handed-off file version on each review card.
Your review card shows the proof version your reviewer received, even if the linked file changes later.
Show which proof revision was sent to each reviewer.
Your coordinator can trace the revision recorded for a proof send, even when its send history was missed.