Knowledge Check Slides not accessible

Hi all,

I have been working on a new e-learning and was working with knowledge check slides.

Yesterday I created a few of these knowledge check slides and today I cannot click on them anymore.

They don't appear in the big view, only the previous selected slide stays there:

When I try to force it by double clicking the slides disappear.

Also when I want to do a preview I get the error message that my publish failed:

Can someone please help?

Thank you!

Cheers,

Liesje