you said it used to work? does your remote desktop have accelerated preview support? some only have software playback, not GPU playback. and maybe toggle video accelerated playback in premiere. does premiere stutter locally? did you change any software settings? try another remote software. can it play back in a video player like VLC over remote desktop? is the cpu maxing out on either machine in task manager? or try turning audio hardware off in premiere or turn external monitor transmit off.