Set language to US English, 50Hz & rebooted
seems consistently silky smooth but saw brief break-up when skipping & scrolling text glitching frequently at 18:52 & submitted diagnostics
Closed app & went back in, glitches largely disappeared but getting intermittent, very brief glitch in text but overall still very smooth at 19:05
Video of the 1st major glitching: https://photos.app.goo.gl/yxUYnoqnZ1tJmyZK6
Video of minor, occasional glitch (about 14s in): https://photos.app.goo.gl/xpmYCf7GsgDEr2sk8
(disregard juddering in above videos, itās smooth on TV)
Changed back to UK language, rebooted & glitching disappeared but juddering returned
Definitely looks like youāre on the right track to fixing it