PPoint imported to Impress, slides delay to appear.

HI! I imported some Power Point files with Impress, everything is ok, but I can’t understand why some slides have a lag from 5 to 15 seconds to pop-up.
I attach one of the presentations.

https://drive.google.com/open?id=1garHcYlvxSFwzX33Wq7F4OmXPdKmRzi1