Turret aggro bugs

Was this an intentional change or is this really a glitch/bug? I noticed it happening to teammates for a few games (random aggro switches seemingly for no reason what soever) but it happened to me for the first time last game. I was Master Yi, I attacked under turret then alpha striked the opponent while galio continued to hit him (I hit first so I had aggro) while in alpha it appeared to drop aggro from me to galio (as it should) but once out of alpha it randomly switched aggro back to me.