You can try this if you want.

Close Opera.

Open up powershell, type:

cd "$env:appdata\Opera Software\Opera Stable\Default\Sessions"

and press enter to switch to Opera's "Sessions" folder.

Then, type:

dir

and press enter to see the list of session files (just for good measure).

Then, paste the following into powershell

Get-ChildItem -File | ForEach-Object { Get-FileHash -Path $_.FullName | Select-Object Hash, @{Name='FileName'; Expression={$_.Path | Split-Path -Leaf}} } > "$env:userprofile\desktop\before_restart.txt"

and press enter to produce before_restart.txt on your desktop.

Then, after you restart Windows, load powershell again, switch back to the "Sessions" folder, paste the following:

Get-ChildItem -File | ForEach-Object { Get-FileHash -Path $_.FullName | Select-Object Hash, @{Name='FileName'; Expression={$_.Path | Split-Path -Leaf}} } > "$env:userprofile\desktop\after_restart.txt"

and press enter to produce "after_restart.txt".

That should give you the before and after hashes of all the session files to see if they changed at all after restarting Windows. If the before and after hashes for each file match, nothing changed for the file.