this has ALWAYS been an issue (even in my x1 setup and back to hs7) when you're moving huge groups of notes like that because the synth is trying to audition ALL of them at the same time. i thought that was pretty funny imho that the software was designed like that. my tips: mute the track when you move the notes, use process/transpose for large groups of notes or - use groove clips set to follow project pitch and insert pitch markers to handle transpositions. if you're just moving the timing and not pitch positions of large blocks of notes, do so in track view by selecting the clips.
EDIT - and the vid plays in chrome just fine.
EDIT 2 - Craziest thing... I just tried this in an X1 project in X1 and DIDN'T get this behavior - which I always used to get. and now, same in x2. i did change a couple of params in the config file though under preferences/audio/config file - usewdmdmaforwasapi set to false, ksuseinputevent to false, extrapluginbuffers to 32, and dropoutmsec to 750.
JUST.PLAIN.WEIRD.