In the sentence -- We thank you for bringing this issue to the board's attention and rest assure/rest assured that the matter will be given its full consideration. - which is correct? Thank you.
Hmm. "will be fully considered" is better, or your "will be given full consideration" are certainly better.
Maybe it's a subtle way to say they don't think it's worth much consideration at all. If you say "its full consideration" it does sound a little ... uh... nonsense-y, but maybe it's their sly way to say "which is none at all"?