It does make me wonder if some brake master cylinders on trads were left with machining swarf in the bores. Not many because it wasn't a "thing" on new trads, but makes me wonder.
It also makes me wonder if a high underbonnet temperature might expand the master cylinder just enough to weaken the seals.
A friend had a new FIAT back in the day. When it got hot, the brakes locked on. I don't recall why but it was a known fault with that model at the time, and the only way he could release them was to open a couple of bleed valves to get rid of the pressure. He did that at the side of the road, until something was fixed........
