This is an educated guess as I'm not sure anyone can give a concrete answer as to this particular show's specific reason, but since it was dubbed, there's a solid possibility that the subtitles are a translation of the English subtitles while the voice over may have been translated by the dubbing team and potentially altered by what the voice over actors could deliver with a decent dub.
In my experience, not all shows are run with a strict adherence to the script. Changes sometimes need to be made for actors to deliver naturally and there is often some flexibility in exact lines. If the same flexibility was extended to the dub team, then it seems quite likely that they would deviate from the exact script translation.
If they are using the same subtitle timing for multiple languages, then it might not have been worth having someone sit through it and dictate the subtitles and try to align them to the proper markers vs simply directly translating the existing English subtitles.