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Seems that you have luck; no short between PPBUS_G3H and other secondary power rail.
I hope you've posted correct readings.
Now you can inject 1V into PPBUS_G3H and see what gets hot.
Using IR thermal camera helps you a lot.
Set lab PSU at max current limit.
5A PSU may not help, but try if no better available.
If 1V doesn't help, slowly increase the voltage.
With such pure short (0.001), 1-2V should be more than enough to detect the culprit.