Atom on Windows FTML extension opens in plain text

I’m pretty sure this was working fine 10 days ago, but I’ve just gone back to my Windows laptop.

Files stored in dropbox with a .ftml extension open in the Windows version of Atom as plain text. With the Mac version of Atom they open as expected.

I’m pretty sure these specific files were created with the Windows version of Atom. I just tested with a brand new file on my Windows laptop and the behavior is the same.

Is there a setting I’m forgetting or overlooked?

In both systems I have
Atom 0.204.0
foldingtext-for-atom 0.4.1
foldingtext-markdown 1.3.0

Edit: In the Windows version if I close Atom, but leave the tab with the .ftml file visible it will load properly the next time I open Atom. If, however, I close the tab before closing Atom, then open the .ftml file from the File - Open menu command the file is loaded as plain text. The Mac version behaves fine, so I’m guessing there’s something in how Windows and Atom interact?

This issue is being tracked here:

Unfortunately I don’t have any way to debug it (no windows). So I’m going to have to ask for help on this one. I’d be grateful if anyone with windows and Javascript debugger knowledge would take a look. I’ve indicated where you should start debugging in the referenced issue.

Works fine with the new build in Windows. I tried with files in Dropbox, on the User/Public folder and from nested folders on C:.