The willow chest is bugged. When placed inside a chunk, it will randomly cause the entire chunk's light value to be set to 0 regardless of sunlight, or any light sources placed down. It took me a lot of experimenting to nail down exactly what was causing the bug, but after going to a fresh chunk without any disturbances post-generation, placing a single willow chest caused the same error. I had 2 bases ruined because of this bug.

An important note in case it matters, I am running a server, not a single-player world. I have a picture attached here for reference.
I have also linked the Reddit post I made when I was bug testing, it has a more detailed explanation of how I discovered the exact cause of the bug.
https://www.reddit.com/r/allthemods/comments/zi27ax/help_weird_chunk_problem_keeps_filling_my_base/?utm_source=share&utm_medium=web2x&context=3