We cannot suggest much with the amount of information provided: you haven't posted any code,
any stack traces, any logs, any information about how message bodies are encoded, absolutely nothing.
This is an engineering mailing list and engineers need specific information in order to reason about things.
RabbitMQ never modifies message body and very rarely injects new headers into messages (typically
plugins do so).
RabbitMQ consumers (subscriptions) are supposed to be long running but if they run into a channel
exception (see server logs) or don't handle exceptions, they indeed won't handle more than one message.