RDP Lockouts when logging into Windows 7 workstation in Server 2012 domain

I have a user who logs in from four different laptops to his WIndows 7 desktop. We recently upgraded the domain controller for his office to Server 2012. Ever since we did so, he's been experiencing regular lockouts (to his desktop computer running Windows 7 Pro) after logging into one or the other of the computers. The laptops are not all running the same OS. One is 7 Pro, one is 7 Home Premium, one is 7 Home, and the other is Windows 10 (Home, I think).

We have not yet established a pattern for what logins will lock him out. Credentials for RDP are saved, and we know they're correct. I re-entered them and tWe're not sure there is one. We suspect there's something in Server 2012 that, by default will not allow logins from multiple computers. NONE are simultaneous login. He's trying to use the same domain account and password on all four laptops. Whether he exits Windows ungraciously, or logs out properly he might still experience a lockout to the workstation on a 2012 domain.

Anyone have any idea?
Dana FriedmanCEOAsked:
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stephen brownnetowrk supportCommented:
Have you checked the security logs on the 2012 DC for information?  Is the AD account actually being locked?  If so then I would suggest checking the key manager on each device to see if there are stored credentials causing conflict.  rundll32 keymgr.dll,KRShowKeyMgr from cmd will show you what credentials are being stored on each device.
Shaun VermaakTechnical SpecialistCommented:

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Dana FriedmanCEOAuthor Commented:
Yes, the AD account is being locked. I checked Key Manager on some of the workstations/laptops, not all.
Dana FriedmanCEOAuthor Commented:
Thanks for your help.
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