Multi doc view crashes app - Important workbook inaccessible

Tried to view a large PDF in multi doc view, app crashed, now the MN workbook is inaccessible (crashes on open each time).
Is there a way to reset to the default view state? I think what is happening is that the MN workbook tries to open in multi doc view each time and keeps crashing the app.

This is important. Please advise on recovery.

Cloning the MN workbook is a workaround…. The original is still inaccessible….