The (open-brace) is being recognized as a separate token (even though it is the beginning of a string of octets) because of a check added in revision 835.2.14 to allow non-numeric text in braces which gmail spews out occasionally. (Where is its bug report?) "5441" is obviously numeric, but there is probably a timing problem in recognizing it. Disabling the numeric check allowed the retrieval to proceed fine.
Similar problem occurred today. vm-imap-tokens shows a log like this:
retrieve
response #<marker at 110199 in IMAP mailhost.c 14:43:44>
object #<buffer IMAP mailhost.c 14:43:44> "*" 110200 (atom 110199 110200)
object #<buffer IMAP mailhost.c 14:43:44> "1669" 110205 (atom 110201 110205)
object #<buffer IMAP mailhost.c 14:43:44> "FETCH" 110211 (atom 110206 110211)
object #<buffer IMAP mailhost.c 14:43:44>
object #<buffer IMAP mailhost.c 14:43:44> "BODY" 110217 (atom 110213 110217)
object #<buffer IMAP mailhost.c 14:43:44>
object #<buffer IMAP mailhost.c 14:43:44> 110219 (close-bracket)
110219 (vector)
object #<buffer IMAP mailhost.c 14:43:44> 110221 (open-brace)
object #<buffer IMAP mailhost.c 14:43:44> "5441" "5441" 110225 (atom 110221 110225)
object #<buffer IMAP mailhost.c 14:43:44> 110226 (close-brace)
object #<buffer IMAP mailhost.c 14:43:44> "Return-path:" 110240
(atom 110228 110240)
The (open-brace) is being recognized as a separate token (even though it is the beginning of a string of octets) because of a check added in revision 835.2.14 to allow non-numeric text in braces which gmail spews out occasionally. (Where is its bug report?) "5441" is obviously numeric, but there is probably a timing problem in recognizing it. Disabling the numeric check allowed the retrieval to proceed fine.