I found this happened today on two of my posts by the same user.
The cause? There are two:
1. If you accidentally double *tap or click the appreciate link, it adds then subtracts the appreciation that was just attributed.
2. If you want to look at who else has appreciated a post, it is too easy to accidentally *tap or click on the attribute link and thereby accidentally either appreciate or UN-appreciate a post.
This has happened to me as a user myself on others’ posts - and numerous times if I am not careful.
I am attaching a screenshot showing this in my reputation history. I have NUMEROUS examples of this in my history. Shame, because I would have had more rep for my efforts here by now.
Thank you