Jetson TX2 frequent shutdown issue

I have a new Jetson TX2 in my hand, just bought few few weeks ago but it shutdowns so frequently, few seconds to few hours (mostly few seconds). To make sure no other interference I had by unplugging USB and HDMI leaving only power plug.
When the power plug is connected, red led(CR5) is on. But after power button is pushed green LED illuminates and turn off in few seconds or a bit longer. Replacing AC adapter to more reliable one I have used for some time(19.5V, 6.15A) did not change the situation.
Once it shutsdown, power button no longer functions. I needed to unplug power plug for few tends of minute to make the power button to function again.
Once when I was lucky enough to flash(install) JetPack and run CUDA programs before shutdown. But as Jetson TX2 shutsdown so frequently, I can not use it reliably.
Is this a software issue or a hardware issue.

Hi, it more looks like a hw issue, do you have any log output before shutdown? You can check the input current with a DC supply and also the temperature of system by reading values of thermal zones as this topic https://devtalk.nvidia.com/default/topic/1032887

Okay, how could I fix this hw issue. As Jetson shutdown in few seconds, access to log is unavailable. So it is not possible to read system thermal values. My room temperature is 14.8C so Jetson is not be in too hot environment. No DC supply w/ current monitor (Is it normal to have one as a Jetson user?).

You can send it to RMA. Our FA team will analyze and fix it or send another one to you.

I have send it to distributor before RMA and they tested but there was no problem. After they returned Jetosn, I have tested with 1K and 4K display. With 4K display made the same issue. Could that be the reason?

Did you test with powerful external cool solution? As it is really like thermal problem.