Page down key not working and Random number of beeps during BIOS startup

[k7at0s]

Recently the laptop keyboard showed a strange behavior. When some keys are pressed in quick succession they function as page down key pressed and held. The actual page down key isn't functioning. The keys so far I've identified are QA or WS or ED or AZ or SX or DC or JN or JM. Also ctrl + home isn't working though home key alone works well. Ctrl + numpad home works well too.

This issue persisted the whole day. Had tried windows troubleshooter, HP hardware diagnostics, uninstalling the device driver, restarting the pc, but to no avail. Have noticed the issue resolved while writing this query. Though it is working fine now I want to know what could be the issue and what needs to be done to resolve the same if it ever repeats in future.

[2022-08-26]

Edit: Now the issue with the keys like QA, WS, etc seems disappeared but page down and home keys are not working. Numpad Home and Page down are working fine.

HP PC hardware diagnostics - component test - keyboard - failure id M4MXGW-660B7E-QFPK1G-G1KT03.

[k7at0s · Accepted solution]

Even the beeps started during start-up (BIOS). Number of beeps initially remained 4 or 5. Once disassembled the laptop just to check and after assembling, number of beeps became very random. Sometimes 15, sometimes 4 then gap then 5. Someone suggested to remove each component and check so started off with the keyboard and it turned out to be the issue. But haven't done any changes w.r.to hardware or software recently. Since pg dn is giving me the issue have removed the key cap and the issue stopped.