Unable to link to sub wikis (from within wiki-page)

I create a wiki page without problems. When on the wiki page I can also create sub wiki (page) without problems.

My problem is that I cannot link to the sub-pages (from frontend editing). If I try to insert a link the editor jumps to the bottom of the screen and I’m not presented to any kind of dialog.

Using backend editing works 100%.

Newest WP. All plugins updated. DIVI theme. Tried to use std wp theme – same problem.