Hi! I already posted this on Reddit, and I thought I'd post about it here too.
I recently purchased an iPod Classic 5th gen off eBay and I received it a couple days ago. I knew from the listing that it had an issue with the hold switch(it was stuck in lock mode). The thing is when I replaced the hold switch/headphone jack assembly, the device still is stuck locked regardless of the position of the switch. Furthermore, the device doesn't respond to any button presses at all, even when I try to reboot/restart or boot it into debug or disk mode(with the exception of if it's connected to my laptop. I've gotten it to reboot a few times while connected to iTunes, though the issue persisted).
It shows up in iTunes and on my laptop when I connect it. I was even able to restore it and add some songs to it(though I'm not able to access them on the ipod due to the issues with the lock). After researching online and trying a number of things, I'm unsure what else to try other than maybe cleaning the hold switch/headphone connector on the motherboard with some Isopropyl alcohol and hoping that fixes it(I should be trying that tonight).