My fireteam encountered a weird potential bug during the Contest of Elders spider tank encounter. We collected 5 of 6 explosive tanks and were able to hack the explosive for the shield. We were then able to destroy the spider tank however afterward we did not get an encounter completion. Attached is the photo of the platform where the spider tank is supposed to be with the 5 of 6 collected still there. We tried to move forward through the prison but were unable to do so. Upon returning to the spider tank room we were able to to the "Begin match" interaction which restarted the spider tank encounter. Upon the next tank pick up it said 6 of 6 however we still had to find 6 individual tanks after the restart. We were able to complete the encounter and are able to move on after the restart. We are unsure why after 5 tanks we were able to do the hack and kill spider tank even though progress was not being recorded.