Duplicate tags when importing Joomla content

I have an issue when importing joomla content to K2.
It seems for every tag it finds it creates a new tag, even if the tag already existed.
Because of this I'm getting a lot of duplicate tags. And going to the tag-url will only show one item.

Is there a way to solve this? I tried looking for a way to merge the tags but can't find one.

I tried reinstalling K2 to reimport the articles, but I get the same issue