Missing Daisho Bug?

[StoneGolem]

Sometimes I clear the entire Castle and loot everything except 1 Daisho and the final chest. Is this a Bug? The Final Daisho is nowhere to be found. This issue has happened severeal times to me.

Solution:
Saving then reloading the game made the missing Daisho spawn.

[Bryan]

for me this happened too but only in a single castle in Omi where Yasukes main story is, only 2 of the 4 Daisho's would spawn inside the big tower but the other 2 didn't spawn outside cause that is still a friendly area.

i think your problem might also be quest related, if there is a quest in or near the castle the Deisho won't be there, after you finish the related quest they should be there again.