From the patch notes a while back the following note was added
Ancient titans
Due to the item pouch system (which was not introduced at the time of the max guild update) ancient shards no longer auto-loot
As a result, ancient shards are now stackable
This is all well and good, however ancient titans drop ashes on every kill. How are we supposed to use a looting bag effectively here?
Turns out the looting bag can still pick up stackables it has even if it's full! thanks @Logical