Caps lock Blinking

[R20231126]

The Caps lock of my laptop is blinking on and off in an irregular manner. No pattern can be observed.

At some times the caps lock stays on or off for a couple of minutes.

When the button itself is pushed, there isn't always a response.

I think this problem started, when I connected a (possibly broken) arduino MEGA with all three of my USB ports.

An other reason I can think of is the possibility of some rain having entered my backpack and possibly damaged my HP laptop.

The BIOS is checked and is up to date.

All hardware tests are a succes.

Connecting an external keyboard doesn't resolve the problem.

[BeemerBiker]

There are 4 USB ports, two on each side.  Do all 4 ports fail when an external keyboard is attached?  If an external keyboard fails to work then hardware damage is likely.  Do other USB devices work such as a Wi-Fi mouse, data transfer to smartphone, usb flash drive?

Does the device manager show any problems?  What about the windows event viewer?

Try reset: press and hold the physical power button and wait five to ten seconds. The computer will shut down and turn off entirely. Wait 30 seconds to allow any onboard memory to completely clear, then press the Power button again to boot back into Windows.  This usually resets the USB failsafe's.

Possibly water could cause a problem but it would dry out in a day or two and would not cause a problem with external keyboard.

check warranty and call for repair info:
https://support.hp.com/us-en/checkwarranty
https://www.hp.com/us-en/contact-hp/ww-contact-us.html

If out of warranty and USB ports defective then a cheap bluetooth keyboard / trackpad is a workaround.

[R20231126]

The blinking of the caps lock is simultaneously on both the keyboard of the laptop and the external keyboard. This is the case for all three USB ports. The fourth USB port is a USBC port and I don't have such a keyboard available.

If the laptop is in bios-mode the blinking is already going on. I think this means that the problem isn't related to a windows-software error. So I assume that the device manager and windows event viewer are unrelated to the problem.