Can you precise which version of Kunena you are using and the Joomla version that you are using.
We never had report on such kind of issue and we don't know the reason.
In the title, you mentioned and issue after Migration.
Can you explain what you migrate and how.
Perhaps that will help us understanding where the problem comes from.
If now, you want that we have a look directly on your environment and potentially debug this strange behavior on your environment, this is still possible with our billable support that you can order at
www.jms2win.com/en/joomla-multisite?page...35&category_id=1