The video works fine in Movie Edit Pro 15 and when I export as MPEG. When I upload to YouTube directly via the Online option on the menu bar the audio in the YouTube version is scratchy, broken, and and unrecognizable.
I do not have Movie Edit Pro 15, but I have 16 and I just did my first YouTube export, to test this with a simple music video image transition. My sound came out fine.
Maybe there are things in conflict during the export for YouTube? Other programs running and such