Sounds like it may have been sending an (off-by-one, inverted, etc) signal indicating it's on a different track, or moving a different direction or speed, than

Sounds like it may have been sending an (off-by-one, inverted, etc) signal indicating it's on a different track, or moving a different direction or speed, than it was in reality. While the press release says these were "in addition to the ones it was supposed to emit", it's not hard to imagine that a similar error could happen where the wrong signals were sent in-lieu-of the intended signals, and thus leave trains rolling that should have detected an emergency-stop situation.