I am seeing this same issue using Emby for Kodi on the Firestick. I am using direct paths playback and seeing it freeze every 30-60 seconds on multiple firesticks. I confirmed that playback was fine using the Emby app on my phone. This started within the last few days (I believe it worked with no issues on Friday). I am attaching both the Kodi and Emby logs in case that helps. Let me know if there's anything else I should try.
embyserver.txt kodi.log