The bug was reported to us last week. I found this thread (https://moodle.org/mod/forum/discuss.php?d=428295), and decided to test,

1- Create a badge in a course (don't even bother about criteria).
2- Add a resource or an activity (I tried feed, page and forum).
3- Delete your resource or activity, go to course recycle bin and restore it.
4- Go to Manage badges. It should be duplicated.
5- Repeat the delete/restore and keep counting.

After playing in our Moodle, I went to qa.moodledemo.net and was able to replicate.