kbielefe

Never mind about the same seed. I tried it again in creative on the same seed and got a saddle in 43 casts.

@nothing999, did you try on the same seed as me? I suspect it might be due to the new reproducible rng.

This is not a duplicate. Iron golems spawning partially inside glass is one thing. Since 1.20 prereleases, iron golems are spawning completely on top of glass with no non-glass blocks nearby.

This bug is being marked as a duplicate of other new 1.20 bugs that are very different. Iron golems spawning partially inside glass is one thing. Since 1.20 prereleases, iron golems are spawning completely on top of glass with no non-glass blocks nearby.

My wife and I both had similar trouble playing the first time on 1.19.4, on separate computers with different operating systems. (One on Windows, one on Linux). Mine fixed after switching skins a few different times in the new launcher. There are quite a few recent similar reports. I doubt this is a tech support problem.

It doesn't have to be a proper fix to make this playable again. Rather than seek to prevent the error, seek to detect the error. Occasionally scan the loaded chunks for a light source with zero output, then refresh the chunk's lighting cache if it is. Based on the symptoms, you might be able to even do this scan just once whenever the chunk is first reloaded (and after sleeping in a bed if that doesn't reload the chunks). I also don't think you have to check every light. In my experience, if it happens for one light, it happens for every light in the chunk. That should make the scan relatively efficient to do. This would also give you a hook to add some logging around when it occurs, which should make it easier to determine the root cause.

I'd much rather have slightly slower chunk loading and/or lights briefly blinking out than going out permanently.

As a warning and for additional info, when I ran the recommended workaround (download, optimize world, upload) on our realms world that was first created in 1.14, it reset everything in the spawn chunks. Not just the lighting, everything we built/placed/mined in the spawn chunks was gone.