station running roscore cannot listen to rostopics from other stations

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We have an issue communicating with rostopics and are looking for a work-around (or at least explanation of the issue).

Suppose station A is running roscore and station B has mapped its ros master uri to station A. Both station A and station B can see the full list of rostopics. If station B publishes a topic, station A can subscribe to it, but it never receives any messages (for instance 'rostopic echo <topic_name>' never has output). If station A subscribes to it, 'rostopic info' will show station A as a subscriber and station B as a publisher.

However, station A can publish messages to itself and can also receive service requests from station B.

Do you know why station A cannot receive messages from station B? Does this seem like a network issue or is this an inherent/intended ROS feature?

In response to mwise_wg, setting the ROS_IP of station A to itself didn't change the behavior. Same with setting ROS_HOSTNAME on station A to it's own name. roswtf returns "ERROR Could not contact the following nodes: * /rostopic_3179_1..." and "ERROR The following nodes should be connected but aren't: