I was up on the orc stonghold and looked down and saw a dragon circling in the valley. I went and fought it - it was elder, my first. After i killed it, no absorb. Reloaded few times to make sure i gave final blow. Later i found word wall some distance away.

Random bug? Will soul absorb start working again?

I had this after installing 1.4 with two Blood Dragons. Both dead but they did not go up in flames nor saw I a soul trap. The third, an ancient dragon, then did give me his soul.

Someone told me that sometimes a dragon soul will not get absorb and that it has been like this since the release of the game. I have never observed this before even though I have killed maybe 50 dragons by now. Hard to say if this is now a bug or just a coincidence. One cannot roll back and check...

Some dragons are static respawns and only in certain places. So if you already killed it once and happen to come across it again later, you can not absorb the soul twice.

Yes, I have killed them all before. They were in those places where there is a dragon icon on the map. I kill them pre-emptively as I do not want them to come swooping down on me, but still, it is the first time I have seen this.

In my case, i suppose i must have killed the dragon before, but i had not found the word wall location yet

I had this problem occasionally before. Supposedly it's on respawns.

Have eaten several dragon souls since 1.4 on my game.