Villagers keep despawing in valid villages

I have been playing on my single player world for about a week now, and within the last 2 days, I found some villagers. I brought those villagers back to my base (which had valid villager houses that I built), and I went to go mining for some resources, and when I got back, they had despawned. weird part about it is that my base is inside my spawn chunks, so hypothetically, nothing should be despawning