This is kind of a show-stopper but it looks like it was never resolved? We're running into this problem right now. Currently running Confluence 6.15.2 and will finally be upgrading to the latest in a week or two so maybe this will be taken care of with that? (fingers crossed)
https://jira.atlassian.com/browse/CONFSERVER-57854
Summary
When using the Multimedia macro to view videos, it might work or not. The video start but stops at a certain time saying that they are either corrupted or run into a decoding problem. It's unclear what causes the problem reported here since it's not consistent.
