Barrier Duration/Stacking Bug

When the Summoner Spell is activated, and then another active Shield is created and stacks on top of the barrier, the second shield will disappear entirely once the duration of runs out.

I first noticed this on Butcher's Bridge, playing . + http://ddragon.leagueoflegends.com/cdn/5.15.1/img/spell/TahmKenchE.png , and once the barrier duration ran out, my entire 2000 point shield disappeared all at once. (rather than decaying or being reduced by damage, it just disappeared)

I havn't tested it extensively, but I now believe this happens every time barrier stacks with another shield. (when barrier runs out ALL shields go away rather than just itself.)