You can close Opera and delete the "Sessions" folder in "C:\Users\yourusername\AppData\Roaming\Opera Software\Opera Stable\Default" to see if it helps. You'll lose all open tabs though.

While Opera is closed, you can delete everything in "C:\Windows\temp" and "C:\Users\yourusername\AppData\Local\temp" to see if it helps.

You can uninstall Opera (don't choose to delete your data when asked), delete the "Opera" install folder in "C:\Users\yourusername\AppData\Local\Programs" that remains, clear those 2 temp folders, download the Opera installer in whatever browser you want, launch it, click "options", adjust everything how you want and reinstall. That might fix it. Not sure as I don't have the issue.