Routing a Google AppEngine cron job to a specific version of a module

I have problems when trying to route the cron job to a specific version of a module. Module batcher contains the cron.xml file. Inside the file I have:

<cron>
    <url>/_user/tags/deleteOld?page=0&amp;pageSize=50</url>
    <description>deletes user's old tags</description>
    <schedule>every saturday 21:00</schedule>
    <timezone>Europe/Helsinki</timezone>   
    <target>v4-dot-batcher</target>  
</cron>

This works ok and the cron job is routed to the batcher module version v4 correctly. Now, if I try to redirect this cron job on another module called mules:

    <cron>
        <url>/_user/tags/deleteOld?page=0&amp;pageSize=50</url>
        <description>deletes user's old tags</description>
        <schedule>every saturday 21:00</schedule>
        <timezone>Europe/Helsinki</timezone>   
        <target>v4-dot-mules</target>  
    </cron>

This does not work anymore, as the request is always sent to a default version (called test) of the module and not on v4.

Is it because the cron.xml is in the batcher module or is this problem related to the dispatch.xml? I have not set anything related to route "/_user/tags/deleteOld" in dispatch.xml of the mules module.

Looking at the Logs, the protoPayload contains:

protoPayload: {
@type: "type.googleapis.com/google.appengine.logging.v1.RequestLog"
versionId: "test"
startTime: "2017-05-29T16:45:00.628537Z"
endTime: "2017-05-29T16:45:00.642901Z"
latency: "0.014364s"
megaCycles: "11"
method: "GET"
resource: "/_user/tags/deleteOld?page=0&pageSize=50"
httpVersion: "HTTP/1.1"
status: 404
responseSize: "234"
userAgent: "AppEngine-Google; (+http://code.google.com/appengine)"
urlMapEntry: "unused"
host: "v4-dot-mules.testapp.appspot.com"
taskQueueName: "__cron"
finished: true

}

The configuration of the v4 for mules looks like:

runtime: java7
threadsafe: true
instance_class: F4
inbound_services:
  - warmup
handlers:
  - url: '/.*'
    script: unused
    secure: always
automatic_scaling:
  min_idle_instances: automatic
  max_idle_instances: 1
  min_pending_latency: 5s
  max_pending_latency: 15s
  max_concurrent_requests: 10

Any ideas about this? Much appreciated!