I escaped the Evoker when it was at position X -6510 and I was at X -6604. But it was still attacking, even when I was at about 100 blocks away. When I was at about 130-150 blocks away, it stopped (probably because the chunk stopped being active), but when I returned to -6620, it attacked once again. You may see in the screenshot that its new summoned vexes flying to me again and again.

Recently, my issue with Evokers was resolved as Invalid, because I was still at its viewing distance. (MC-164827)