The parser is handling multi-line comments inside hex strings incorrectly. Let's use the following rule as an example:

rule TEST {
    strings:
      $ = {
            01 [5]    /* comment 1 */
            02        /* comment 2 */
      }
    condition:
      all of them
}

The rule is correct, but the parser is returning the following error:

unexpected RBRACE, expecting BYTE or MASKED_BYTE or LBRACKET or LPARENS

This is because the once the parser finds the opening /* for the first comment, it greedily consumes all the characters until the closing */ in the second comment. This causes the 02 byte to fall inside the comment, so the parser is actually seeing the string as: { 01 [5] }, which is syntactically invalid.