musicstate 3.21 / Joomla 3.6 / menu item issue

Hi ... using latest musicstate / Joomla 3.6 (gavick quickstart template)
If I´m in the backend and want to create a menu item, I creat "new" ... I already see an kind of "empty" overlay down in the left corner (see screen 1) - I continue, want to select an item, if I do, I get an white overlay with no content in it. Cannot proceed from there. Check the screenshot sequence with the last screen 4 ... what is "sbox-window" for ? that looks like the overlay ? Thanks

issue resolved ... even so I cleared cache and closed browser ... a few minutes FF crashed, started, and then it worked like it should

Hi

Ok, Thank You for this information. I'm closing this thread now.