This known error applies to users of the browser Chrome.
Chrome users may experience that preview suddenly starts opening in the same tab as the source test, question or question set.
This is caused by an eager popup blocker in Chrome, and is easily fixed. Go to the following address:
chrome://settings/content/popups
Add the URL to your Inspera site to the allowed list in this format:
Note that the above is an example, and you must use the URL to your Inspera site for this to work.