Sounds more like an issue with your remote access configuration.
What information is showing in the “now playing” tile for such a remote stream on the Plex server dashboard? I’m specifically interested if the stream is listed as Remote or Indirect — indirect streams run through a relay server of Plex because the client/server fail to communicate directly; those indirect connections are limited to 1 Mbps (2 Mbps for Plex Pass members).
https://support.plex.tv/articles/200871837-status-and-dashboard/
If the stream is indirect, you might want to review your remote access setup.
Did you already have a look at the related troubleshooting support article?
https://support.plex.tv/articles/200931138-troubleshooting-remote-access/
There’s also a guide with some more details on how to troubleshoot remote access issues.
