Slimes not spawning?

In creative mode again, I hollowed out another 5 chunk by 5 chunk volume directly below the northern half of the volume I listed above. Again I lit up the surrounding volume, this time between layers -40 and -35 (plus above and below, outside this volume). Again I put glowstone all around the volume, and waited 24 blocks above the center. No slimes.

So then I created a superflat world in creative mode, to see what would happen. Slimes began spawning immediately in several nearby slime chunks. So, at least in superflat, slimes spawn normally.

NOTE: I checked what appeared to be the slime chunks (where slimes were spawning) against ChunkBase's slime finder (https://www.chunkbase.com/apps/slime-finder#-8289529590777600243), and the chunks where slimes spawned matched that site's predictions. So, it isn't the algorithm for determining whether a chunk is a slime chunk that's the problem.

Now, in addition to the volumes I listed above, I also previously hollowed out several slime chunks, as reported by ChunkBase's tool. But, I chalked the lack of slimes off to a change in the algorithm in C&C. That appears to have been a rabbit trail for me, but it does clearly show that there's a basic spawning problem for slimes (and who knows what else).

Whatever the problem is, it may only affect "real" worlds. I.e. worlds with normal seeds and structures.

I have now seen three slimes spawn underground. They were all in a giant cave, so I couldn't tell if they spawned in slime chunks or not. But, in designated slime chunks (per Chunkbase's tool), I still haven't seen any spawn.

Perhaps the algorithm changed?

Is this still an issue in the latest prerelease (1.17 pre-3)?

My superflat is filled with slimes, and slimes in superflat spawn in slime chunks. I cannot reproduce the issue.

Yes it was still an issue at pre3. I started a new world at vanilla 1.17 (without the datapack), but I haven't gotten far enough yet to know if the slime chunks are working or not. If they are (I suspect they will be), then I'll test 1.17 plus the datapack to see what happens. I'll report back after each set of tests.

Regarding superflat, see my first comment, where I address this. In superflat, it works as it should, and the slime chunks match the algorithm (that was at one of the pre-release versions). So, I think the problem is more fundamental; it's only happening in "real" worlds.

I'm not sure how it affects large biome worlds, or other non-standard worlds. And, I never install any resource packs or datapacks other than the ones released by Mojang, so I don't know if running a modded world has the same issue.

DO NOT CLOSE as a duplicate of 226064 when that was already closed as a duplicate of this one!

And the game is so unstable with the datapack that I have been unable to tell whether it is fixed or not. So it shouldn't be closed naturally, either (yet).

This problem appears to be fixed at Java 1.17.1 with the C&C datapack. I haven't tested it against 1.17.1 without the datapack yet, though, so don't close it quite yet.

I spoke too soon. In that test two days ago, one slime spawned in four chunks (of which three are supposedly slime chunks) in an hour of real-time. But, I went and tested a single slime chunk in the same world for twelve hours, and no slime.

So, I would guess either the algorithm for slime chunks changed, or the spawn rate is extremely low compared to what it used to be.

I'll do more testing, but this is still a problem.

I am unable to reproduce this issue in 1.17.1.

The problem is fixed at 1.17.1 vanilla. I won't be testing snapshots anymore until there's a stable 1.18 snapshot. So, I think you can close this ticket. I'll open a new one against 1.18 if I see it there (once it's out).