Quest reward not granted – Lithara, The Wayward Spear

The quest Lithara, The Wayward Spear is marked as completed on the map, but the quest reward was not granted.
The boss did not drop the Gemcrust Skull, so I did not receive the +40 Maximum Spirit.

Avatar name: VysokeNapeti

Current Spirit: 60

Steps to reproduce:

Complete the quest Lithara, The Wayward Spear

Defeat Lithara

Quest completes, but no Gemcrust Skull is dropped

Expected result:
Gemcrust Skull drops and grants +40 Maximum Spirit.

Actual result:
No Gemcrust Skull drop, Spirit remains at 60.
,

60/100 means you have 60 available out of 100. You have some gem enabled that is reserving 40.