i think i agree with the dude above, it could be a technique thing so make sure you land with the fist correctly
i see you mentioned about wraps may be too tight/loose, why not try looser or tighter wraps next time you work the bag and see if thats the case? but always make sure you wrap them the right way and land punches the right way.
why not try longer wraps, that way you can get more support especially around the wrists. what are your bag gloves like? are they decent weight 'Gloves' or just 'Mitts' (little gloves with no solid thumb covering and no wrist velcro/lace etc)
At the end of last season my left wrist got dodgy when i threw a left hook on the bag/pads (but not sparring+fighting) and the problem went away when i changed from a standard style hook to landing my left hook with like thumb facing the floor instead of the ceiling if you get me, basically landing with an upside down fist and landing with the knuckles as opposed to the tophalf of fingers and the knuckles. Although its not all doom & gloom as landing hook this way scores points in am. boxing as you land with the white part of the glove more.
Loll and sorry for hitting you with what looks like my lifestory was hard to describe that hook haha