Before the self-check, I was able to use the L2 button, but once I started the self-check, I couldn't press L2, it stopped responding, and it stopped. After that, L2 became unusable. I shouldn't have done the self-check. Even after updating the firmware, the symptoms did not change.
In the same way, in the self check, it stopped at L2. I replaced the main board with another new one and it cleared the self check. So I think it is an initial defect of the main board. I bought it from amazon, so I returned it to amazon as an initial defect.