Impact 4.8.3
Minecraft 12.2 [Forge]
Baritone ?.?.?
When I call #version it says 'null version', although some time ago I'm pretty sure it said 1.4.* when I called it.
The only other two mods I use are WorldEdit and Schematica.

When trying to fill something that is presently water, baritone fails. The exact behavior depends on wether the water blocks are flowing.
Flowing:
Just pauses with 'Unable to do it'.
Not flowing:
Goes nuts placing and removing throwaway blocks.

Might also depend on buildInLayers, because when I set it to false the behavior changed very slightly.

I've had the same issue at times on some servers.

#okIfWater, #buildIgnoreExisting

That doesn't solve it. This just makes it ignore water. Obviously, the intended behavior is for it to replace the water as opposed to ignoring it.

Set both to false.

When both of them are set to false, the intially described issue occurs.

Why isn't there an #okIfLava?

Because it hasn't been added. Why are you commenting on a random issue?

Because I'm trying to use #sel fill but Baritone keeps deleting my lava.

Why are you commenting on a random issue?