Blue buff not attacking you [GAMEPLAY]

When i play jungle, i am always put off by the fact that the blue buff will sometimes just not attack me after the first couple auto's, wait, then attack me again. This usually happens with lee sin where i will q over wall and blue will attack me but not minions, also when i go evelynn i will attack blue buff and it will just stop attacking me, staying in a fixed position as if stunned.