For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Looks like board tries to start and restart because T2 detects a problem; possibly short on a secondary voltage.
All USB-C ports have the same behavior?
PPBUS_G3H drops when swithces from 5V to 20V points to problems with some secondary supply.
Is also possible that one I/V SMC sensor is triggered and SMC cycles power.
Can you turn it on in SMC bypass mode?