As a dealership tech and shop foreman for 25+ years I've seen a lot of the finger pointing of blame,vehicle comes in for repair and comes back with a unrelated issue (you rotated my tires now my phone won't sync you must have done something to it🤪) Sometimes it's just bad timing things break...
I did this repair on mine just before warranty was up,is a very common repair i've done on the 4 and 6cylinder engines (silicon sealant doesn't seem to like extremes in temperature that we get in frozenland)
I had a simular issue on my 21 2.3l a/t,was pulling my new teardrop trailer home and at highway speeds a deer jumped out from ditch applied brakes and no assist at all! Turned out it was a bad vaccuum line to engine.the 2.7 is a different beast as it has a electronic booster.
Not sure why they haven't responded to you but when one of my mudflaps broke in half they replaced it,It took a little while to get to me because they were out of stock at time(2weeks)
This looks like a good power solution for my cameras,but might have to do modifications to work with my AR rail but hey i'm always up for a challenge.(makes for good content)
I hear you man, I will be doing the harsh shift TSB on mine(and installing a PPE aluminum pan) as soon as I clear out some of the 10R's I have apart already.(That'll teach ferd to be in cahoots with GM!)