I don't know if anyone else has had this happen to them, but i recently received a quest to kill the dragon a Bonestrewn Crest and the dragon is bugged beyond all belief. It tweaks out in the air and basically has a seizure in place. I tried to kill it with my bow, but as soon as I got it down to the point where it has to land it flys off into the distance out of my range and when it glitches back (usually flying backwards) it has full health. I have the new patches so PLEASE for the love of God fix that stupid dragon.

It's a bug and they are aware of dragons that fly backwards. They promised a fix sometime next week.

Elder Scrolls: Ass Dragons

Doesn't appear to be just the dragon. I killed one there (nothing unusual there, got the soul too), but the word wall turned out to be a dud. A second dragon (presumably respawned) was killed there, but this time I didn't get a soul.

Also have an issue with this dragon. Glitched animations and freezing in air. I've gotten him to zero health and he keeps flying and attacking. His health bar just disappeared. I've used the console to try to kill him and not even killall affects him.

Patch 1.2. That's your answer as to why right there.

To AzSteve, I've noticed that static spawned dragons tend to give you their souls once, and the next spawn in that location doesn't, but random spawned dragons give me a soul every time. Try fast travelling a few places. Esp with a horse. Dragons love horses.

That dragon ate Faendal.

However, the patch dictates you must wait for revenge.

Which version are you running? (Edit - sorry, I reread your post and you are using most up to date version)

I've had Steam offline for a while so am still running the previous version of the game but that dragon still exhibited weird behavour in my pre-patched game - at one point I wandered past there on my way to Riften and he was flying round and round his little outcrop and I couldn't get him to engage me in combat so gave up and wandered off, when I came back 3 in game days later he was still flying round and round roaring and not engaging any of the nearby giants or mammoths - I eventually managed to kill him with arrows but when he finally crash-landed I didn't get a soul from him.