Chris O'Brien

I just had this happen on my Realm. I bred two horses and their child had 14 hearts, 3 of which appeared empty/dark. I tried to heal it with apples but I just mounted the horse. If it took damage I could heal it, but only to 11 hearts. When I left the area and came back, the empty hearts were gone and the horse just has 11 hearts, so it seems like the max health is working correctly, it's just showing extra hearts that aren't really there.

Edit: Actually, I'm pretty sure this is decreasing the health of horse offspring, and the missing hearts represent hearts that should be there. I keep breeding two horses, one has 11 hearts and one has 13, And I'm consistently getting horses that have 10-14 hearts, but 3-5 of those hearts are missing. This is making it much more difficult to breed a great horse, which really sucks when a recent update was aimed to make horse breeding more viable.

It wasn't happening very frequently for me so it could still be a problem, but as far as I've seen so far this is resolved. It's worth noting though that the lighting requirements for mob spawns didn't change for sky light in 1.18 (just block light), so this could still be happening for sky light.

I've noticed this in my beacon mine, where I have a torch grid layed out so there are 5 blocks between every torch, and they're all on the ground (I've noticed it in parts of my base that were spawn-proof before as well). Mobs spawn very infrequently, but it still happens. They're not falling from the ceiling or anything, I've watched them spawn, and it looks like they're only spawning in the middle of each square of the grid, so I'm guessing the problem is that they can spawn at light level 8 now. I've only noticed it in the 1.17.3 update.