Don't know if anyone else has run into this glitch but I completed all 12 of the Craglorn caves/dungeons. I received the point achievements for each one except the Lower Craglorn Cave Delver which gives 15 achievement points for completing them all. For some reason the only one checked when opening up the Lower Craglorn Cave Delver achievement was the Tombs of the Na-Tatambu all the others that I had completed were unchecked.