Unclickable Ritual Altar,figured out the reason.

So I have farmed ritual for long time, several times ritual altar remains unclickable.

The reason for this is, there is this monster that burrows in the ground,its mostly prevalent in sand orientated maps,it has squigly antenas that stick out of the ground when its burrowed and untargetable.

If this monster gets killed in the ritual area the ritual altar will remain unclickable.