Visual items that "hangs"

The published course was delivered to the client. It was working very nicely on my own computer (WIN10), however, when the client runs it on their computer there are visual elements that "hangs" from one slide to the next. 

It seems to be a file size vs computer / processor problem. 

The suggestion from the client is to compress the file and this way making it more easy to handle for a less powerful processor. 

Any suggestions would be highly appreciated. For example how do I compress the file? Are there (better) alternatives? Could be another issue than the file size that causes the visual elements to "hang"? - If so, what and how can I fix it?

Thank you!