At first, after every night, the Ethernet link was down. A simple reboot would help. Then the links down became more frequent. Now, even a reboot doesn't help. Sometimes the Ethernet connection would establish after reboot, but would disappear after 1 minute.
I'm disappointed
try changing the cable, as a first step of the troubleshoot.
What's on the other end of the connection?
after 8 months of use
Aside from the question, what is connected to the other cable end, this question: is the device still under warranty? Usually these devices have 2 years of warrany. Contact your seller if cable is ruled out as problem. It could be a hardware defect.