Adobe Acrobat Reader shuts down after dragging a tab / an open file off the ruler

Why does Adobe Acrobat Reader shut down when I drag a tab / an open file off the ruler?

I used to be able to do that, and upon doing so Acrobat Reader would open that file in another Acrobat Reader window AND keep the other file(s) open in the original Acrobat Reader window.

Now when I do this Acrobat Reader shuts down. When I reopen it, it tells me it shut down suddenly and asks if I want to restore the files I had open.

I often use this method to compare (2) PDF files side by side for design purposes.

NOTE - I am using a Dell laptop running Windows 10, 64 bit. View attached video showing what happens.

View video - Via Loom showing Acrobat Reader crashing when I drag a tab off the ruler