York 2-pass Chiller Surging

[furikazashi]

I have loads of data which I will be uploading after I write this post. Starting about 3 weeks ago my chiller has been surging to the point of shutdown for safety. I have the option of running another chiller side by side with it but it seems to make the problem worst sometimes and go away others. I cannot tell what is causing these issues but AFAIK but i've had a YORK technician out several times, his best guess is that it happens when its under a higher load. The pump strainers are clean there is good flow throughout and there is no air in the system to my knowledge. I will attach a 7 day running log of good statistics to pair with 2 other surge kickout logs of what the system looked like when it shutdown. Any help would be appreciated.
On a side note: one thing I do notice is the approach temperature when the chiller gets shutdown due to surges is that the Approach temperature is in the negatives, which i would believe improbable since at a full load it should run about 3°F and with nothing should be 0°F (unless im mistaken I'd be happy to learn more.) Is it possible for the approach temperature to be able to shut a chiller down? I don't see any points for it.

Chiller Specs
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