I am also experiencing this bug. I started Kiel’s on tier 2 thinking I could get the whole achievement. I completed the other trial first. Now I cannot complete Tier 1. Also, when I join the instance, it automatically assumes Im on Tier 2. Not sure if this is an issue or not, it may just select the highest youve completed. It is clear, however, when I am doing Tier 1, due to the quest info in the top right.