Try this registry setting on one of the PCs to test to see if it works.
If it does not then I would call this a 'bug' and would recommend that you send feedback to Microsoft.
Go to regedit.
Go to...
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\UserSwitch
Set UserSwitch to 1 to turn it on
Reboot.
If the UserSwitch key is not there then create it and set to 1.
Now sometimes this will reset back to 0 so link below explains how to set a task to run to keep it at 1.
http://woshub.com/how-to-show-all-users-account...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
Let me know how you make out.