My Up Dpad isn't working

I had the similar issue so here is the solution log

Issue:

Steam Deck D-Pad "Up" button stopped working. Instead, the Steam and Quick Access ("...") buttons acted as if the "Up" direction was being constantly pressed. Problem persisted even in BIOS, so not OS-related.

Symptoms:

• "Up" on D-Pad unresponsive
• Steam and Quick Access buttons behaving like D-Pad Up
• Input was stuck in a loop, spamming "Up"
• Occurred even before boot (in BIOS), so not software-related

Fix (worked for me):

1. Powered off the Deck completely
2. Opened the back cover
3. Located the D-Pad ribbon cable (marked “D-PAD” on the daughterboard)
4. Disconnected the D-Pad ribbon cable from the connector
5. Booted the Deck with the cable disconnected to confirm buttons behaved normally again
6. Powered off, reconnected the D-Pad ribbon properly
7. Booted back up — everything worked normally again

Theory:

It might not have been a physical connection issue. The BIOS input controller may have glitched and started misinterpreting D-Pad input — causing "phantom presses" and remapping behavior. Disconnecting/reconnecting the ribbon cable likely forced a soft reset of the controller's state. So the root cause may be firmware-related, not hardware failure.

Conclusion:

Bad input state or firmware glitch caused phantom input. Simply reseating the D-Pad cable forced the controller to reset. No need for cleaning — just unplug–replug.

Hope this helps someone avoid replacing half their Deck.