Xotolan, High Priest boss burrows underground and won't re-emerge

Journey's End zone, encountered league mechanic and the boss got to ~80% hp and then burrowed underground and won't re-emerge to continue the fight.

He will, randomly, pop out and follow me around the area, but is immune to damage and will simply re-burrow.

bug id: 1,642,818,099

Bump, still happening.

bug id: 3,332,924,586

I have encountered this bug as well, on the Vaal Temple.