Buffer issue with Roku Streaming Stick+



My Roku Streaming Stick+ (using WiFi w/ the server on Ethernet cable) is constantly buffering (I can watch maybe 10 seconds of a movie at a time). Changing from direct streaming to transcoding has no effect. I have placed a variety of devices (iPhone, iPad, Nexus) next to the same Roku stick and they work fine, so I don't think the issue is signal quality or my server. I can stream DirectTV Now on the same stick in HD without issue. Seems to be unique to Roku - any ideas?

On a related note, I'm also a victim of Plex version 6.14.1 on my FireTV stick, so that doesn't work at all for Plex. I am getting beyond frustrated with Plex. I subscribe to PlexPass in part to support the engineers working this effort but, at this point, I'm starting to feel like a sucker...