Yesterday one of my favorites folders expanded to include repeated entries. I was on build 130 at the time that I think this happened. It appears that the additional entries in the folder came from classic Edge favorites or my Android Edge favorites. For classic Edge, I have some computers on Windows 10 1809 and one computer on Windows Insider 1903 (Release Track).
What makes it particularly strange is that this only occurred in one folder and not in the other folders.