Attacked while Gaurd is Active

As title states, I have been attacked with my gaurd active. This isn't the first time this has happened, but before hand I wasn't positive my gaurd was active. Now I know for sure, I attacked which ended my shield. I had a 30 minute gaurd, closed my phone and then a message appeared that I was being attacked. Watched the attack live, and when it ended I had 21 minutes left of an active gaurd.

Has as anyone else experienced this, it's kind of bullsh*t.

Am I misunderstanding the purpose of an active gaurd, preventing being attacked with no penalty when attacking others?

Let me know.

It's impossible to do that.. whether you have 2+ accounts G++.. so if someone atack that appear ok