Message with nested repeating group and missing delimiter tag is silently ignored

problem

When a message is received that has a repeating group inside another repeating group and the first group is missing the group delimiter, the message is silently ignored. The reason for this is that an InvalidMessage Exception is thrown and the sequence number is not incremented. Normally, this is OK for messages that have a wrong checksum or length because it is expected that the problem "corrects itself". However, a missing repeating group delimiter should be considered a user or FIX engine problem and we should hence reject the message with a meaningful description.