It is HP, and the output of the provided adapter does 28V 5A, so in spec.

With some of the other 28V 5A adapters I have, it charges until triggering a compute heavy task and then stops. I have seen reports online of people seeing this behavior with the official adapter. My theory is that the laptop itself does not accept any ripple at all.

Ah my bad. Are you sure your cable can do 140w? That was the source of most of my pains trying to push 100w to my work laptop. Baseus and Anker have some good PD3.1 chipped cables that worked for me. What kind of charger are you using?