Users can't comment on posts on timeline in groups

I have a closed group and when I post on the time line in that group, others members of the group see the post but only have the options so "Like" or "Repost". They don't have the "Comment" option. I have searched and can not find any setting that would stop them being able to post comments to an item. This has just been pointed out to me today and it may be it has only become an issue since I updated to the latest version yesterday?