4K Buffering Problem via Network

I'm having playing via network. Both my laptop and X9s are connected to the same network. 1080p movies play just fine, but when it comes to 4k videos, there is consistent buffering every 2 seconds and the video is choppy. The problem is usually existent when playing via network. I tested the same files via USB, and playback is smooth.

Have you guys already resolved this issue?

Thank you!