It sounds like the LB is stuck.
It might be as simple as opening it up and reseating the button, or it might need a switch replaced.
The Steam Deck seems to be built to be serviced, I replaced the drive in my OG 64gb LCD model to a 2tb one in about an hour by following a YouTube tutorial.











Once upon a time, people were against social security because they believed the government would use the individual numbers assigned to everyone as a form of identification…
History may not repeat itself, but it rhymes.