Mobs spawning in high light levels

Does the issue only occur on a realm, or does it also occur on the downloaded copy of the world?

I have only observed it on a realm, but haven't spent a lot of time out of spectator in the downloaded copy. If I have time I'll AFK with a villager standing in the middle of the room on the downloaded copy and see if it is zombified when I come back. I don't know if this matters, but there is a lot of lighting updates that happen in that area, such as redstone lamps turning on and off. That area is a portal-based gold farm that is pretty large, and I know sometimes other realm members have some lag in that area. Thank you for the quick response.

If you are only using redstone for lighting, there could be times when there is no light, particularly if there is a lot of lag. It can also be helpful to use other lighting sources around large redstone projects to reduce those lighting updates and the consequent lag that comes with them.

I do have other forms of light in the area, the redstone lamps simply raise the light level at times. The whole area never drops below light level 5, even when all the lamps are off.

I just added a video of mobs spawning and walking around on a well-lit roof. There is glowstone under each of the pillars shown it the video, as well as some scattered torches. (Light passes through stairs in bedrock) This is the same area as before, but much higher. Also, night had just fallen, so any mobs not already chasing me are likely where they spawned.

Having this issue in other areas of the realm, spiders and creepers chasing me on login when nobody has been on for a while, and it is mid-day. Also observing weird stripes of light, I'm assuming on chunk borders, that have no source.

Hi

Would it be possible to attach copy of affected world?

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I don't think I can, as the world is pretty large, around 1.1 GB. Would me loading the affected area using structure blocks into a separate world work? If so, I would need some time to get the files and transfer the structure.

It hapeens on realm or high ping serwer and no this Will not happen on cpied world whem you are not playing with firends

Had a creeper kill me on login in the middle of the daylight a few days ago, still an issue.

Hi

Do you use any behavior pack's?

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No behavior packs were used, nor any mods. One of the realm members uses a texture pack client-side, but other than that vanilla Minecraft.

Added another video, with a creeper that just spawned on top of/ next to crying obsidian.

Hi

Can you upload screenshot that shows Realm world settings?

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The realm also recently has had the player sleep percentage changed to 1%.

Added video of creeper spawning with torches around.

Hi

Copy of affected world would be very helpful. If it will exceed file size limit you can use OneDrive or similar file hosting service and share link.

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Cleaning up old tickets: This ticket had been set to 'Awaiting Response', but has not received a response from the reporter (~3 months+) so is being closed as Incomplete. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines which includes steps to reproduce the problem.

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Still occurring in 1.21. Was building and mobs kept spawning around me, even though it was the middle of the day. Should clarify it was raining, not thunderstorming. Attached video of issue.