According to the official wiki, illager patrols should only spawn within 200 blocks from a village and near pillager outposts. Having this in mind I built my own settlement outside such boundaries and the /locate command tells me the nearest village and the nearest outpost are both 1000+ blocks away. I don't have any villagers in my own town yet illager patrols keep spawning in the middle of my base several times in a single play session which seems like a huge bug.