The unresolvable chunk
A chunk beginning "the second approach is preferable" cannot be represented by an embedding, because what it refers to is in a different chunk. It will match poorly, and on the rare occasion it is retrieved the model has no way to interpret it.
These are invisible when you look at the source document, because the referent is right there on the page. They only appear once you look at chunks in isolation, which is how the retriever sees them.
What each flag points to
Mid-sentence starts and ends mean you are splitting at token indices rather than sentence boundaries. Opening pronouns usually mean overlap is too low. Very small chunks mean the size is below what your content can carry.
Pointer-only chunks — "see above", "refer to the previous section" — should be merged into their neighbours or dropped from the index entirely. They occupy a slot in every result set and contribute nothing.