[Espressosaurus]

Even a single hardware iteration intended to be a drop-in replacement in some cases won't be due to relying on implementation-defined behavior that is not guaranteed by the datasheet and wasn't considered a constraint by the people designing the silicon. Sometimes it's a bug, sometimes it's just "didn't think that was important".

Either way, you're left with something where the saturation behavior changed, or it's no longer possible to read out a value without risk of corruption since they assumed it can be treated as write-only, or some other hard to find and debug problem.

Swapping out chips is an exercise in testing and risk management, and never should be done without care, even before we start talking about safety critical applications.