As the title says, the console detects that the select is being pressed and the analog moves down without being connected....

When I turn on the psp all the LEDs light up but the screen does not. I have not found what error it can be, when plugging...

As I specified in the comment of the other answer, what has partially solved the error and has allowed me to use the buttons without the select has been to clean the motherboard of the embedded dust that was on the back. Although I can use the console, it still detects that the button is still pressed, it may be because I have only cleaned it without isopropyl alcohol and just gently brushing the board. I leave the link where I found the answer, in case someone has a similar problem with other buttons, since it does not necessarily have to be in the same buttons. Lastly to keep in mind, it is likely that if after cleaning with isopropyl alcohol the problem persists, it may be due to a short in the plate. For my part I can't check that as I don't have the tools or the knowledge to see where it may occur. Specified link