There can be several reasons for this. It could be an old v5 plugin that should be disabled or you might still have v5 menu items for this. It could also be caused by a template override.
There may be a few reasons why this issue is occurring. It could be due to an outdated v5 plugin that needs to be disabled, or possibly due to remaining v5 menu items. Alternatively, it could be caused by a template override.
Is the v5 version still installed on your site? Or do you have any template overrides? If so, please attempt to disable them and see if that resolves the issue.