Endermen who've been looked at will no longer agro on endermites

Example; I put an enderman in a box, he is angry at an endermite. From a distance i look at him, he walks towards me but a minecart picks him up. He loses agro on me, the machine puts him back at the endermite, but he will not agro at the endermite

Supposed to be wireless transmission; look at him, he moves away from the endermite and into a tripwire. i can't think of why it doesnt work, i tested for a ages. Once he has switched targets he forgets about the endermite

Wouldnt surprise me if this is intentional to stop wireless transmission, but it feels like a bug.