Chronicle of Lost Memories bugged

Issue: Chronicle of Lost Memories doesn’t not create the last unknown memory.

Example: On my hunter, only Rylakstalker’s Fangs is missing. Upon using the Memory, the cast is initiated and when finished, nothing happens; no red error, the item stays in inventory.

In addition, said memory doesn’t drop from SOA either. Having farmed approximately 20 SOAs on normal, heroic, mythic and m+, there hasn’t been a single drop.
Changing specs also did not work.

That seems decidedly odd. Memories are a 100% drop chance from dungeons now. Are you absolutely sure that you don’t have the memory stashed somewhere in your bags or bank?