Targeting GPU by screen arrangement

I have a Windows 10 machine with 2 GPUs. The primary display is a Quadro k620, the secondary is aQuadro M4000 configured with mosaic for a 7680x1080 display. I start Touchdesigner with -gpuformonitor to lock it to the Quadro M4000. I have the network on my primary display and my output window targets the M4000. When I go to perform mode, i see that the primary display GPU (k620) is being utilized 100% even though the performance appears on the M4000 GPU, and the video is dropping frames/dragging. If I move the network onto the secondary display at the moment when I enter into perform mode then M4000 handles everything and it runs smoothly.

I would think that with GPU affinity it wouldn’t be necessary to do this. Is there a way to work on my primary monitor and enter perform mode without having to drag the TD instance onto the secondary display first? Is it possible there’s something wrong with my configuration?