Test case:

delimiters "$","$"
d1 ::= [
  "p": <%hi%>
]
main() ::= <<$d1.p$>>

Should produce
hi
But instead produces
%hi%

The problem seems to be in STGroup.java method createSingleton. If it is a BIGSTRING it trims 2 chars from each end otherwise it trims 1. But it doesn't take into consideration BIGSTRING_NO_NL which also needs 2 chars trimmed.