External Storage SMB Problem

Nextcloud 17.0.6
Ubuntu 18.04 Virtual Machine on Hyper-V

The external storage goes to a Windows Server 2016 shared folder through SMB.
When I play a video file from that external storage through nextcloud I get ~8-9 Gb/S traffic between Nextcloud and Windows server 2016 ! Sometimes the disk activity on WS is 0 and I still see 8-9 Gb/s. The RAM on WS is not changing so its not from RAM Cache.
There is no problem downloading the video, the traffic is normal.

This is from WS