Guild Wars 2

Hi I just beat the Legendary Skeletal Lich and got the gold reward/karma and experience for defeating him but I didn’t get the achievement and there was no chest or anything?

Has this happened to anyone else?

It has (not me) and not just the Lich. AFAIK they are still “investigating”.
Some people have reported that killing it a second time got them the achievement, not sure if that was in the same instance of a different one.

I have just beaten him again and managed to get the achievement along with the chest.

It’s extremely buggy right now, I had to log out and then back in again because none of my skills would activate. But thankfully managed to get it