I just killed my 6th or 7th dragon, but the last one I killed, is different than the rest. Once it is killed, I can collect its inventory, but it doesn't "dissolve" into just bones. I can walk right through it as if its not there, but when I use a firebolt or something on it, my spell will knock the dragon back. I have loaded a couple saves and killed the dragon at least 5 times now and the same thing keeps happening. For anyone else that has had this problem, what can I do to fix it? Will it fix itself, by that I mean, will I be able to collect future dragon souls, or am I no longer a dragonborn and should start a new game. Any help would be greatly appreciated!

This is a known bug, Bethesda is aware of it, if you are killing the same dragon it will not give souls try to find one in a area you have not been

Thanks for the reply! I didn't know that dragons would respawn once killed. Oh well, at least I was able to get dragon bones and scale.