Exporting under version 5.1.1 doesn't work.

Certains slides are not appearing in the final outcome whatever the export format used. Those slides are greyed out with a diagonal strip in the middle.

I re-downloaded release 5.0 and ensured that it was not overwriting version 5.1.1.
Release 5.0 is not a beta version and was stable regarding exporting/sharing. However having done this and tried to export/share a slideshow I obtained the same problem, i.e. certain slides are grayed out with a diagonal strip in the middle.

I created a new slideshow with the version 5.1.1 and used the export/sharing facility. This time it worked and all slides were exported without any problem.
However, when using a previous made slideshow under version 5.0, the export/sharing facility is not working as some of the slides are greyed out as indicated earlier.
Could this issue been clarified please.