I'm sure there are tons of bugs, I was told a few stories by people in aerospace industry. But I think they cannot survive if they don't keep the number ultra low, because they can't fix it (well except microcode level).
It's a testament to those unsung heroes that most high-level language users can remain blissfully unaware of how much is automatically fixed by compilers in their emitted instructions.
"When PA12 is used as GPIO or alternate function in input or output mode, the data read from flash memory (bank2, upper 1MB) might be corrupted."
I can't even imagine the head scratching one might go through if hit by this, particularly late in development process (when the firmware becomes larger than 1MB).
There are so many bugs in features you never heard of, just like software. It is inevitable given the complexity.