Identified the problem.

The issue is plain text is eating the line break so paragraph is failing since it expects a line break at the end.

src/parser/util.rs

@@ -71,16 +71,19 @@ pub fn get_consumed<'s>(input: &'s str, remaining: &'s str) -> &'s str {
 /// A line containing only whitespace and then a line break
 ///
 /// It is up to the caller to ensure this is called at the start of a line.
+#[tracing::instrument(ret, level = "debug")]
 pub fn blank_line(input: &str) -> Res<&str, &str> {
     not(eof)(input)?;
     recognize(tuple((space0, alt((line_ending, eof)))))(input)
 }
 
+#[tracing::instrument(ret, level = "debug")]
 pub fn trailing_whitespace(input: &str) -> Res<&str, &str> {
     alt((eof, recognize(tuple((line_ending, many0(blank_line))))))(input)
 }
 
 /// Check that we are at the start of a line
+#[tracing::instrument(ret, level = "debug")]
 pub fn start_of_line<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
     let document_root = context.get_document_root().unwrap();
     let preceding_character = get_one_before(document_root, input)
@@ -103,6 +106,7 @@ pub fn start_of_line<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'
 /// Pull one non-whitespace character.
 ///
 /// This function only operates on spaces, tabs, carriage returns, and line feeds. It does not handle fancy unicode whitespace.
+#[tracing::instrument(ret, level = "debug")]
 pub fn non_whitespace_character(input: &str) -> Res<&str, char> {
     none_of(" \t\r\n")(input)
 }
@@ -116,6 +120,13 @@ pub fn exit_matcher_parser<'r, 's>(
     peek(|i| context.check_exit_matcher(i))(input)
 }
 
+#[tracing::instrument(ret, level = "debug")]
+pub fn always_fail<'r, 's>(_context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
+    Err(nom::Err::Error(CustomError::MyError(MyError(
+        "Always fail",
+    ))))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;