Stuttering when playing 2 player

I am still testing when this comes up, however, when I play in 2 player mode, I notice it stutters a little bit, intermittently while playing. Most of the songs I have all have a video with it, so I will be trying some some without videos to verify if its part of the issue or not. So not the entire time, but comes and goes. When I play just 1 player mode, via keyboard or dancepad (using a usb arcade encoder in the pad) it is much much better. Not 100% smooth, but enough to where it does not mess with me. I tried with 1 pad and a keyboard and 2 pads and the issue persists. I normally see it running around 500+ FPS if vsync is off, and I run it in 4K. Does not matter if I turn it down to 1080p, nor nothing much else that I have tried. I have used a loading program as well in the background to load the process up as well (though it was set to below normal for its process affinity).

I have tried Stepmania 5.0.12 as well, which is mostly smooth, like if I played just single player on 5.3 Alpha 4.8.2.

Any thoughts?

So found it was due to the game drawing much more power on the GPU (GTX 1080) than the older 5.0.12 and then it looks like I had a PSU going bad as when it was drawing 60w+ of power, I would get coil whine. Should have a replacement PSU next week and then will re-test.

OK so I got the new power supply today, and now it is smooth as butter, even after changing it back up to 4k! Odd power supply issue, but glad it got sorted out.