I converted my Photoshop elements 13 DVD to ISO then when trying to install it from mounted ISO on DO11 give some weird errors
installing through explorer works fine. Odd thing is once I've run it through explorer I can then run it from DO fine while the ISO is mounted. If I unmount then remount and run through DO without first doing it from explorer it gives those errors.
Try going to Preferences / Zip & Other Archives / Archive and VFS Plugins and disable ISO there. That would have been overriding what double-click does in Opus.