capture a barb camp, but notified as destroyed by someone else

[Syailendra]

one small annoying bug. Yesterday i played a game using poland, and capture a barb camp targeted by almaty. The city state already capture almaties worker, and i chose to free them, but i only got friend status, and the notification shows that the barb camp is cleared by someone else.

 

[Browd]

Are you sure you cleared the right camp?

 

[Syailendra]

yes i'm sure. FYI, i park a scout besides it to heal before last strike, and almaties archer destroy the defender, i walk the camp at my turn. Is that of any effect? Did i miss a patch or something?