“the pro shield doesn’t really have issues playing anything on old or new player”, humm, well, this is not the first time an issue has surfaced, see Frame drop/stuttering on Shield (2017) in latest player update - and there are people on there with the 2019 Pro who had issues (there was a specific release I think in this case that got pulled quite soon after) - so the pro shield HAS had issues in the past - I suffered from this issue, rolled back to the earlier release and that fixed it - it’s only recently that again issues have surfaced.
As for the media - it stutters on anything I play on it, but only with the new player enabled - with the old player it’s fine - and I have tested any stuttering media on several different players (directly using VLC on a Mac, DuneHD player, Apple TV etc etc) all without issue, so I don’t really think it’s media related, but I will upload details so it can at least be eliminated.
And if it turns out to be something specific to my overall configuration (it may be for example because I have Jumbo Frames enabled), well great then hopefully somebody else can benefit from the knowledge.