Iteration Fatigue!

Aside from comments that are only about fixing typos and similar errors, all comments should be considered "suggestions." Just because one reviewer wants something said or done a certain way doesn't mean others will agree. 

If possible, establish one person who has "final say." After collecting comments from the group, that person should go through the review file and indicate which comments to implement. This helps solve conflicts before you make the edits. And, hopefully, it'll help you avoid re-revising the same piece.

If there just isn't one person who has that power, it might help to set up a meeting to discuss comments and decide which suggestions to use. 

Be sure to stress at the start of each review cycle what people should be looking for -- and what has already been approved (and will, therefore, cost extra to revise). That's especially important for audio and video scripts. 

Hi Marguerite. That's a very frustrating but also not uncommon challenge many of us face. It's time-consuming for us to reconcile all those edits. Plus, the agency is spending a lot of time on reviews and may be able to get a similar level of accuracy for a lot less work.

I'll second everything Judy mentioned and add on to her list:

• See if you can narrow down how much of a course each reviewer looks at. If a person's area of expertise just applies to, say, 6 of the 10 lessons in a course, you can save their time and yours by having them just review the content they're subject matter experts for.
• Collaborative editing tools can be your best friend. For instance, if three people can do their edits simultaneously in a place where they can see each other's feedback, work out conflicting feedback themselves, and not replicate efforts, that's way more efficient than each making edits separately. Review 360 is fantastic for this. And if you're just working on text documents, collaboration tools like Google Docs can be a huge help too.
• Start all projects with a kickoff meeting that outlines in writing your timeline for reviews, who is doing what at each stage, and (related to Judy's tip) who can make the final call when review feedback is at odds with each other. Having this all in writing at the start prevents any confusion. But it's also a good negotiation tool. Because a lot of times organizations don't realize how convoluted and time-consuming their review process has gotten until they see it mapped out. So seeing it in writing may make them scale back how many people are involved and/or how many layers of reviews happen.
• This will only work at some organizations, but consider framing scaling down the review process as a time and cost-savings approach. Right-sizing the number of reviewers and review passes can get a course that's still accurate but at a lower cost to the organization (both in terms of budget and how people's time is used).