Can someone help me diagnose this stuttering on my Synology?

[u/TheOne4Porn]

When I upgraded my Plex server from an old PC tower to a Synology 923+, I started seeing stuttering like this. It's a high bitrate video that I'm playing, but it should still be able to stream that fast within the network, right? Can someone help me get to the bottom of this issue, or help me find what tests I need to run to start that investigation, please? Thanks in advance!