I've been having a recurring problem with IB where one of the orders in a OCA group randomly (?) fails to transmit. Sometimes this means that one of my stops or targets doesn't get sent which is irritating, often this means that the entire group doesn't get sent which is worse. I've sent several e-mails to api@... and after advising me to turn logging onto DEBUG, they haven't replied. When I check my logs and the DEBUG logs of TWS, the working & failing orders look the same but for the failed orders I get the error message code 135, "Can't find order with id =". I'm using the same code to send all of my orders so it is a real mystery why sometimes I get these errors and sometimes it all works smoothly. IB isn't any help. Has anyone here seen this before? Does anyone have any suggestions for debugging an app like this - the DEBUG logs of TWS aren't shedding any light and the error logs of my app don't give any more info either.