Why does my armor re lock after I unlocked it?

My security shoulders keep on re locking, can someone help!!!

The security shoulders unlock after having earned 800 gamerscore but they are very glitchy so more often then not people get them without having 800 gamerscore so just get 800 if you don’t have it already

I have every achievement in Halo 3, but my Security shoulders still lock sometimes and don’t show up in multiplayer. Halo 3 has always been glitchy.