Loss of connectivity after copying/extracting data from NAS

Hi,

I have a WD My Cloud Ex2 with a Firmware version 2.11.178. When I try to copy into the NAS a couple of Gb of data (photos, videos, docs, etc.) from my laptop, the connection of the NAS to my LAN gets completely lost after some time in the process of copying. After this, the NAS is not even reachable pinging it in the terminal and I have to reset it each time to get it back into the LAN. Additionally, I´ve noticed that the copy rate in this process fluctuates considerably even going to zero for some seconds, and not reaching more than 10 Mb/s when connecting the laptop using a network cable.

What can I do to solve this issue?