Ritual - Blood Filled Vessels Not Dropping

Hi,

Just noting that I have "Sacrificial Due" node allocated on the Atlas Tree, which gives a 15% chance for the last altar in a map to drop a "Blood filled vessel", and after 200 ritual maps completing all rituals, I have dropped zero. This would be quite unlikely statistically.

All of these maps have been T16 Crimson Temple rare maps with Eater of Worlds altars active.

Is this a bug?

Thanks!
Tim