Machines hang after MS Windows 10 KB4535996 Update - Worry-Free Business Security Services 6.7

Multiple machines become unresponsive or freezing after MS Windows 10 KB4535996 Update in Worry-Free Business Security Services (WFBS-SVC) 6.7

Root Cause

Windows Defender cannot recognize the WFBS-SVC agent as AV defender properly so it tries to lock a file when the WFBS-SVC agent wants to open and scan it which will cause the interop issue. At this time, it is determined that this issue may be related to Windows patch KB4535996.
tmxpflt had interop with Windows Defender from the memory dump.

While some users have experienced problems trying to uninstall KB4535996, these are the steps that you need to follow:

In Windows Desktop Search, type update history then click View your Update history.
Select Uninstall Updates.
On the Installed Updates dialog window, find and select KB4535996, click Uninstall.
Restart.

You can also download Windows Update troubleshooter, which will enable you to block KB4535996 proactively / stop it from reinstalling.

Turn off the machine.
Turn on the machine and enter in safe mode.
Open the command with admin permission.
Enter the following commands:
- "sc config WdFilter start=disabled"
- "sc stop WdFilter"
Reboot the machine.

Tap on the Windows-key to open the Start Menu.
Type regedit.exe and hit Enter.
Confirm the UAC prompt to continue.
Navigate to the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender
If you see the preference DisableAntiSpyware on the right, double-click on it and set it to "1" to disable Windows Defender.
If the preference does not exist, right-click on Windows Defender and select New > Dword (32-bit) Value, and name it DisableAntiSpyware. Once "DisableAntiSpyware" is created, double-click and make sure the value is set to "1".
Restart the PC.