So, i triggered a raid in my world in Minecraft 1.15.1, i won it, but didn't get the achievement ''Hero of the Villager''. 

I was killing an Evoker in the last wave, when suddendly, the Raid progress bar vanished. I killed the remaning Pillagers, and didn't receveid the achivement.

It was very frustrating, cus i used all of my diamonds repairing my armor and sword.

There was a point that i went a little distant from the village, just to escape from the Evoker. I thought that would have triggered it, but i've a lot of videos on the internet of people going far away from the village and the Raid kept running.

The villagers didn't died, they were all protected.