diff. PvE/PvP/WvW Builds and Elite Specs
As far as I have seen it now saves specs, so it may kick you shield off but once you re-enter WvW it will revert back to your WvW spec.
I know you have a sperate saved build for pvp pve and wvw. That is the reason for the problem. If my wvw spec alows me to pick up a shield because of my elite specialization in wvw and i join pve where I dont have this elite specialization. The shield gets kicked out of your equipment.
So if i go back to wvw then i have to search the shield somewhere in my inventory to equip it again.