to locate the problem, some more information are needed, e.g. configuration of the device, topology about the connections.
In addition, the information like the version of the image and which RevPi are you currently using are also needed.
Other available information are also welcome.
Before I get the concrate informations, I can give you a guess. Have you configured the 2 Eth ports with the IP Addresses in the same network segment. If you do so, it is possible to happen so.