The video literally shows there is nothing active on tabs or sidebar of screen in version 3.1.2.
There are very few reports of similar problems over the past four years.
The most common reason for no activity within SumatraPDF is either a poor file that most frequently causes a rendering issue or another application is locking the files / the SumatraPDF file handling process.
If it’s one or a small group of files they may be faulty and can be posted to GitHub(Issues · sumatrapdfreader/sumatrapdf · GitHub).
If it’s related to a file location such as Dropbox or Google Drive then it is an OS issue.
It usually happens to me. I have tried many versions of the program and still happens. In this case they are powerpoint documents converted to pdf. Nothing special I think.
If it is a group of similar files
powerpoint documents converted to pdf.
and they affect more than one version, it could be the conversion or machine
try reading them with portable copy on another pc,
If they still freeze then it likely the converted content.
If that is the cause then how are they converted?