Usually, you can turn in your opponent's hourglass Athena flag to the Stranger when you've matched as Guardian vs. Guardian. However, I ran into the same bug that there was a reddit post about recently, where even without a merge, the flag is a normal flag and not won in battle, and cannot be turned in. I believe this has something to do with when the flag item is created, ie. where the ship sinks. My opponent ran out of bounds while they were dead and on my ship, and I was also on my ship, very far from where they sank, so no players were around to see the flag coming up from the wreck. I think this may be a reason that it comes up as a normal flag, since it was very far and may have generated after the fight was concluded, thereby not being part of the fight (like it usually is). It's only a sample size of 1 but there could be some connection here as to why it is bugged, so I hope this might help it get fixed!
Hourglass Athena flag won in battle unable to be turned in
1 out of 2
