I know there are several threads here about Prime noises, but I think these are different. Either way, I had taken the car in for several noise issues that were verified by the technicians: Qi mechanism noise: This one, I addressed here: "Clicking" sound under the center console | PriusChat Clicking noise coming from the front axle area: When I was driving slowly in a downward angle inside a parking garage, I would hear a rhythmic clicking noise when braking. Definitely a click per rotation of the tire and only when braking at a downward angle. I reported it as a clicking noise similar to that of a worn axle boot, so I guessed it was the axle. Originally, the technician couldn't replicate it and I had to do a drive-along to show him. I managed to clearly show him the issue and he originally diagnosed it as the brake caliper pins not engaging? I disagreed but whatever - he was the expert. Resolution: They confirmed that it was indeed a bad front axle. Apparently, axles (or a specific part of an axle) was on back-order, which makes me believe that it's a common enough of a problem. Said it was safe to drive on and the noise only occurs with the combination of forward momentum and downward weight. Somehow the part came in quickly and got it fixed quickly. A "thump" from the rear when coming to a complete stop when braking: When I came to a complete stop, I would hear a slight thump from the rear. Louder with a harder brake. I also had to replicate the noise with the technician. The noise sounded like it was the rear drum brakes. Resolution: They confirmed this noise was normal and from the suspension that they also confirmed on the Primes on the lot. I actually heard the same noise from a loaner Mirai.
I had a similar thump from the rear. They actually diagnosed it as a loose bolt on one of the suspension components. They tightened it up and the noise has completely gone away. Of note, the noise first became noticeable around 2K miles, I had them look at it on the first 5K inspection and that's when they fixed it. Tech seemed to know right away what the issue was so it may be fairly common.
From the thread title, I thought you were going to report a transaxle that obsessively goes into heretical mode.
Maybe something "lost in translation"? If that's literally what he said he's in need of a refresher course, lol. Caliper pins are the components that simultaneously hold the brake caliper AND allow it to shift side-to-side, nothing fancy. That sounds better. Back order would say to me it's an uncommon problem, that they don't bother to keep it in stock. Either way, it's resolved, and that's good. Regarding the two quotes above, I believe there's a Technical Service Bulletin on it, loose bolt in the rear suspension, up near the top.
