Frequent intermittent pauses when playing video on new QNAP Plex server

Were you ever running it successfully on the previous version (1.17 etc.)? The problems you’re describing sound suspiciously like those that I and some others started having just after updating to the PMS version you’re running (1.18.0.1913) - you may want to take a look at the thread below, just in case something similar is going on with your server: