Hello,
Just to clarify, the network switch behaves the same way, and the port goes down after around 2 minutes? Perhaps there is some physical damage to the port?
If possible, I will ask you to perform a factory reset and check if that helps.
If other devices and cables exhibit the same behavior on that specific port, then the device will most likely need to be returned for warranty repair, as there aren't many other options that can be tried.
Best regards,
DaumantasG