On a couple of sites, and one PC per site - both Win10, we are getting the below message. To clear it the user has to repeatedly click the ok button about 30 times before the users is logged in normally.

We think it is related to Doc.manager. As if we un tick the Doc.man option in User Profiles, get the user to log on and back out again, tick it back on then no message appears again, but after a number of days it comes back!
Any ideas would be appreciated.