Can't get into RCM mode, Switch won't get detected

I have recently bought a second Switch on ebay, seller claimed that he refurbished the console. The serial is low and matches the serial shown in the Settings, Serial was checked and therefore it is definitely unpatched.

It's from 2017, so it's a bit older than my other Switch which is from summer of 2018.
Everything is setup for injecting a payload to a switch on my laptop. The other switch is instantly recognized via usb in TegraRCM...
I have 2 different jigs that work without any problems on the other switch, which is in auto rcm atm..

There is no reaction to plugging in the switch via usb on my notebook, the other switch will popup as APX regardless of being in the home menu or in TegraRCM.
I'm doing it like i ever did before (entering RCM...) but nothing seems to work. The switch will look like being in RCM mode and is not booting horizon os but does not get connected..
I tried the SX OS payload injector which also will not work..

I've opened the switch and had a careful look, the right side of the USB port part on the motherboard
looks a bit melted.. Maybe it was already replaced once but it was a shitty solder job..
I also suspected that there might have been a trinket m0 installed, which I couldn't find so that can be striked out as an issue too..

My guess is, that it's the USB C Port... might be partially broken, when i look inside the port it looks a bit melted..
The switch is useable in the dock, will charge battery with cable or docking station connected.. So has anyone a clue or had the same experience?

 

Thanks for the reply, i've sent it to a repair shop to replace the usb c port but the guy mailed me and told me the usb port is fine, he checked the values with a multimeter... It looks a bit molten to me but what do i know..

I will definitely check it out myself once the switch has come back.. Seems like others have the same problem recently...

 

I was unable to ocate any shorts by checking around the switch with a multimeter, I uses M other switch to compare. I noticed that the switch won`t charge the battery but it will work docked.

I stillt hink its the USB c port, that one looks molten and looks like someone tried to replace it but may have failed.. The rapirshop guy said that he checked everything and there would be no need to replace it, but I think he didn't want to work on a botched USB port that someone else already tried to do.. My 2018 switch has a water damage sticker the faulty 2017 one doesn't have one......... Not ure if someone took it off or if the 2017 switches didn`t have one