Bug cause revit hung

[jimho]

I see, I forgot that I had changed the file name to 1A.rvt(since within it the link mode changed to attachment, so it is a little bit different from the original 1.rvt)
You can simply use the button “reload from” (at the botom of your second image) to replace the 1.rvt with the new 1A.rvt
Or another way maybe easier: just simply rename the 1A.rvt to1.rvt then the revit can load it automatically.

Hope this may work for you.
Sorry for the inconvinient,

Jim