You have not upgraded to 4.8.6
I would suspect your not uploading all the right files or your ftp program is not allowing you to overwrite files.
That 4.8.5 comes right from 4.8.6 pp-inc.php
I even pulled up your upgrade file and its old.
I would delete all the main scripts except config file and try uploading again. Something is not allowing you to overwrite the files and this will cause an issue