You can write bug-free software, so long as it doesn't have to do anything useful. And, even if the software doesn't have bugs, the hardware it's running on does. And, even if the software doesn't have bugs and the hardware doesn't have bugs, the specifications for the software have bugs. And, even if none of them have bugs, the other systems you're talking to have bugs.
Which is likely what this thread subject is all about. They will probably just tweak the FADEC to accomodate it somehow. It will be a little harder to modify an input, but that is always an option.