What is the reason for this to happen? Is there any way to fix it besides redoing it?
There is no line creating a face right there!
My discord for more information - “! ʳᵉᵃˡ 𝐄𝐡𝐎𝐆𝐫𝐚𝐮 ᶠˣᵖ ✞🐊#9189”, help me please
Hard to say from just your screenshot. Looks like it could be Z-fighting, two or more overlapping planes sharing the same position in space.
Upload your .skp file to get a definitive answer.
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