Looking in to this issue you are experiencing it appears to be a known issue with ActivInspire keeping the embedding of the video you have inserted. I will pass this to the software development team to review and hopefully implement a fix in the future.
For the moment, I would recommend re-creating the flip chart and not inserting the video. You should be able to copy the content on each of the flip chart pages (minus the one that initially had the video) into a new flip chart so that this will be a smaller file size for you.
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