App course damage

Me and user “valdemar085” were creating a course:

and after making some changes valdemar085 is not able to load his course on mobile app. After making a single change in his another course:

the same problem appeared and he’s not able to even open it on app. The reason why the 2nd change in course had to be done was no sound after few first words.

What should he do? Will next changes couse same defects?

Marcin