in a circuit breaker context, we are trying to publish rabbit messages in a "headers" exchange. We're using the AMQP publish connector (version 1.7.4) in mule 4.4.0, and we're trying to publish our message with headers. The message ends up being published but the headers disappear for some reason that we don't know

The subflow containing the publish connector :

<sub-flow name="publish-retry">
        <amqp:publish doc:name="mom_provider_config" 
            exchangeName="${secure::exchange.delay}" requestBrokerConfirms="true" config-ref="domain-amqp-provider-config">
            
            <amqp:fallback-exchange-definition removalStrategy="SHUTDOWN" type="HEADERS"/>
            
            <amqp:routing-keys>
                <amqp:routing-key value="#[vars.originalPayload.routing_key]" />
            </amqp:routing-keys>
            <amqp:message>
                <amqp:properties correlationId="#[vars.notificationId]"  messageId="#[(vars.retryCounter as Number) + 1]"/>
                <amqp:headers ><![CDATA[#[{
    "nb_retry": (vars.retryCounter as Number) + 1,
    "routing_key": (vars.originalPayload.routing_key splitBy  ".")[0] ++ "." ++ (vars.originalPayload.routing_key splitBy  ".")[1]
}]]]></amqp:headers>
            </amqp:message>
        </amqp:publish> 
    </sub-flow>

    <sub-flow name="publish">
        <amqp:publish doc:name="mom_provider_config" 
            exchangeName="${secure::exchange.event}" requestBrokerConfirms="true" config-ref="domain-amqp-provider-config">
            
            <amqp:fallback-exchange-definition removalStrategy="SHUTDOWN" type="TOPIC"/>
            
            <amqp:routing-keys>
                <amqp:routing-key value="#[payload.routing_key]" />
            </amqp:routing-keys>
            <amqp:message>
                <amqp:properties correlationId="#[vars.notificationId]" />
            </amqp:message>
        </amqp:publish> 
    </sub-flow>

any idea on what might cause this ?