I have quite-similar? issues on similar setup.
Windows 10 - i7 - 8Go RAM - Quadro P1000 - SSD - 3 FHD projectors - MM 3.7.1
I am playing one 5760x1200 .mov HAP video at a time and I have really random audio and image stutter sometime <1sec sometime ~2sec, sometime once every 3 minutes, sometime every 20sec... really random.
The only noticeable thing I see in ressources monitor is a peak in disk usage every time it stutters.
I don't have everyday access to the computer so I won't be of big help testing things but I'll try. Next step is trying to lower video reolution a bit.
I have exactly the same setup running 10h/24 6j/7 in a museum since january with MM 3.6.4 but only 5040x1200 video and it runs smoothly.