Spontaneusly lit areas in 2b2t?

I've played a bit on 2b2t and during night I've noticed a few areas which are apparently spontaneusly lit: I managed to find no torch, no lava, no glowstone, no jack-o-lantern, but there was light anyway.

Is this a known bug? Is it random or it is somehow triggerable?

Such a bug is only visual, or does it affect also actual world behaviour? (i.e. mob spawn, crop growing, etc.)

Example:

Solution 1:

Glitched lighting due to failed light update.

Minecraft doesn't recalculate lighting of blocks all the time, only when events that have a potential to change it happen. Otherwise, light level is one of properties of every block, stored, saved to disk, restored as you enter the area with given block, generally persistent.

2b2t runs on a Spigot or derivative server, not vanilla - and the server has a number of optimizations aimed at reducing the excessive lag typical to 2b2t. queue-light-updates is a Spigot property that allows distributing queued light updates over time, reducing lag as a lot of updates at once could really slow the server; something similar is a standard in vanilla since version 1.14.

That means, light updates don't follow immediately, as the events that require them happen - for example, player breaking a torch - but are deferred to when the server can catch up to them. They are scheduled to be calculated, and the list of pending updates is only kept in RAM. If something happens that disrupts the process, for example a server crash - the update is forgotten and the world lighting remains in an invalid state.

Due to chaotic, secretive and non-vanilla nature of 2b2t, it's unlikely this could be replicated on purpose there, but for 1.15-1.16 vanilla, a reliable, if complex, technique (that does involve crashing the server at specific point!) has been developed to replicate this, and much more complex effects.

Light suppression explained

Showcase:

Solution 2:

Put a block IN where the light starts, try to make a "UPDATE" in the place where the light is in.

Sometimes, when we put a lot of lava and put water INSIDE it and OUTSIDE it, the lava just turn to obsidian but keep doing light, the things i just did is to put blocks in where the lava WAS and the light just goes out.

PS: It can be server problems or your minecraft bugged out too. Try to reload your server or even your minecraft.

If the problem continues, do what SevenSidedDie just said: ask for a friend to investigate personally.

If it still continues, well, i dont know what to do anymore =/ At least i tried to help.