captivate / windows / freezing / heavy file

I can see that English is not your native language, so I need to ask some clarifying questions:

• Are you saying that this module is 600 megabytes in size?
• Are what you call 'animations' actually MP4 video files added to the project?  
• Did you only test this module by playing it from your own computer hard drive as HTML5?

From the issues you describe it looks like your module is too heavy for the available bandwidth your customer is able to deliver from his LMS.  He is finding that the videos (if that's what the 'animations' are) cause playback to stall because the browser has to wait for more video file to download before it can continue to play.

The reason the videos work better the second time is that the first time it buffers until the video files have been downloaded completelty.  When the same project is played for the second time the videos are already completely downloaded and bandwidth is not an issue.  But this only helps that particular user, not all the other users that also need to download and view the videos.

This buffering problem is quite common if you have a lot of heavy videos added to a project.  If possible, the videos should not be 'download videos' but be streamed videos that are actually on a Media Server (e.g. Vimeo) and then you just have links to them in the project.