NTLM/Kerberos authenticating device instead of user

So since today only, we are having a strange issue, where users are getting authenticated by devices instead of username. 

This is how it should look, and for most users it is correct it seems.

So the above, its basically their username@company.net which works fine.

But some users are getting authenticated by device, like this:

I've never seen this before, but its blocking all web access since we use web policies that block web access if the user is not in specific AD groups. Obviously as a computer object, these are not going to be in the correct groups.

Any reason this would be happening? Seems to happen more in Chrome than other browsers too.