It seems that the promotions hinting sight and hunting sight 2 miss the appropriate unitcombat tags.
I filled in unit hunter and do fine now.
But there are promotions which need to be tweaked or to be more precise, prereqs wich need to be altered.
Some buildings or wonders give free promotions to all units, for example a zoroastrian wonder grants free morale promotion to all units built in this city.
On the check for the next promotion you don't fullfill the prereqs and get this morale promotion removed, since Morale needs promotion_leader as a prereq.
Same for the free speed promotion out of the riding school. Speed needs flanking 3 and combat 3, so if you don't have enough points to promote your units up to the prereqa you'll lose this promo on the next promotion upgrade.
DH's militia promotions are also removed in the process of the next level up.
I'd suggest that you either check the new to achieve promotions before they are applied and leave the existing and free given promos as they are or rearrange the promo checks for not to remove free promotions.
Most people do like to keep the hard earned promotions, at least i do.