Which process is crashing? Is it dopus.exe or something else, e.g. docsvw64.exe?
Excel and PDF viewers are not part of Opus; Opus merely hosts whichever viewers are installed on your system. The reported names also come from the viewers themselves, and are displayed so you can tell which components are being used.
Adobe have not updated the name of their viewer component in over a decade, as they are slack. Other PDF viewers may be faster for you.
Which viewer name is displayed when you view Excel files?