Keyboard stops responding on Dell Latitude E6430

I have a corp Dell Latitude E6430. After windows boots up, after sometime the keyboard does not work. No key press is recognized. Sometimes keyboard works for a long time, some time it does not even work at initial login

I connected a external keyboard and it works just fine. I ran BIOS diagnostics, also the keyboard appears in device manager without any issues.

I think its not a hardware issue, its some process/service or a keystroke that is disabling the keyboard.

What could be the issue ?
 
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