Not sure if this is actually a bug, but I discovered that it if you name the export folder (or any parent folder of that export folder) with an ampersand, and try to save it as the location where you want to export your BSS website files, the text in the in the box will turn red, and the export button will be grayed out.
HOWEVER, you can still click the Export button from the main menu, and it will export the files to that folder! Very strange.
Removing the ampersand(s) resolves the issue.