Hi everyone ,
There seems to be a wired bug concerning looting Strongboxes in Random Battlegrounds , so i will provide 2 links explaining there importance in game as they are one of the most important sources of legendary drops.
the bug description : Only Golden Strongboxes seems to drops from Rated/Unrated Battleground wins but any lost bg (no matter what the losing team did in bg should be rewarded according to their performance explanation down below) : these is not the normal case it is discourages players to not participate ,stay afk or leave bg .
source : A Guide to Legion Legendaries - Guides - Wowhead
Bronze ,Silver ,Golden Strongboxes Blue Post : https://us.battle.net/forums/en/wow/topic/18194084739