This is at the forgotten shore on the ship with the radio thingy. Kill the enemy group at the ship, go to the location visible in this video. Wait till the grenade cooldown is ready again, then jump high enough till the enemies spawn. This way you can spawn a new group every ~30seconds. I really hope they fix it for release. I think triggering such easy respawns of enemies that can be killed with a single grenade and sometimes a bit extra work should not be possible, please fix it for the release.