The PGN standard gives {, }, and ; special meaning in some but not all contexts which complicates parsing when a comment contains one of these characters. An example of the problem can be seen with the following PGN text.

<pgn>1. e4 {A comment; with a semi-colon} e5 ; A comment {and an aside} with curly braces</pgn>

In the comment after e4, the semi-colon should be parsed as a plain text semicolon because it is inside a curly brace comment. In the comment after e5, the curly braces should be parsed as plain text braces because they are in an end-of-line comment. The parser does not do this, and instead gives them their special meaning in all contexts resulting in the comments being cut-off prematurely or including text that is not part of the comment.