Goto the URL opera://about, take note of the "profile" path, close Opera and delete the "Sessions" folder in the profile folder. This will wipe out all windows and all tabs (and islands) in all workspaces, but it might fix the crashing.
If you need to save your open tabs first, right-click a tab, goto "save" and choose "all tabs to a speed dial folder" (and repeat for other workspaces you have if any). Then, when you start Opera back up after deleting the sessions folder, you can right-click that speed dial folder and choose "open all in tabs". This will not restore the tabs back into their islands if you had any grouped into islands.
That's the first thing I would try.