A solution is to ensure you don’t have any steps of the Xal’atath quest chain in your quest log. You will either want to abandon it or finish it. That was the solution that fixed it for me & several others.
Link to a thread where we discussed it a few months back:
A couple people chimed in that they weren’t on the quest chain, so either they didn’t understand or they might of had another quest-phasing issue. All I know is, once my quest log was clear, the phasing issue was gone.
The solution should be to de-conflict the issue, but until then I hope this suggestion might help you out. Cheers.