Ran an elder rift with 10 purple crest , fought the rift gardian next to a book lectern on the edge of the map. When the chest opened , only 4 gems dropped for my 10 crest.
In addition to a description of the bug you are reporting, please provide:
Device Type: PC
Device Model: Alienware Aurora r15
Device Operating System: win11
Diablo Immortal App Version: 3.1.0.2341201