Numlock does not work unless I unplug and replug keyboard after reboot

I have had this problem on three different keyboards, from three different brands on two different computers.

After a reboot, the numlock will not work. The indicator light goes on and off as expected, but I only get numbers - the arrow keys do not work, no matter what state the numlock key is in.

If I unplug the keyboard, wait moment and plug it back in the numlock key functions as expected. Then a few minutes later it goes back to only doing numbers. A second keyboard "reboot" will usually make it stay until the next computer reboot. Sometimes I have to do it a third time.

All of the keyboards with this problem have been have been high-end mechanical keyboards like the Corsair K70 I am using now. When I upgraded my home computer to Win10 (Razor Blackwidow keyboard), the problem went away. No such luck on my office computer.

Any ideas?
Brad

It is solved!
Turns out that Webroot Secure Anywhere intentionally, and with malice aforethought, disables the numlock key in web browsers. I have no idea why.
They have had a registry hack fix for a few years, but my googling never encountered it until now. But the Win10 anniversary update negated the fix!
Good news, they have a new one. Here is the message and link from their tech support:
Hello,

Here are the instructions for the registry patch
I hope this fixes the issue for you. If not please reply with any error messages that come up and I'll look into it.

http://download.webroot.com/IDShieldNumLock.exe

If the tool is run without arguments will modify the registry and prompt if ID Shield now has control of Num-Lock (Enabled) or if ID Shield no longer has control (Disabled). It will then ask for a reboot to complete the process.

If the tool is run with an argument it will be run silently (for example: though Agent Command - Advanced - Download and run a file). Pass it one of the following arguments:
· -disable turns OFF ID Shield's control of Num-Lock (meaning it is now Disabled). The following are also valid arguments (/off, -off, /disable).
· -enable turns ON ID Shield's control of Num-Lock (meaning it is now Enabled). The following are also valid arguments (/on, -on, -enable).
If the tool is run with two or more arguments nothing will happen.

To note the registry key that this affects is HKLM\SYSTEM\CurrentControlSet\Services\ikbevent "DWORD":Type 0x01 with this key in place ID Shield's control of Num-Lock is disabled and with it removed it is enabled.

Regards,
The Webroot Support Team