The ideal test is to have access to two or more gateways in range of this mystery device of which you have yet to reveal any hints as to its origin.
Then, with both the gateway internal logs and the TTS console for those gateways open, send.
If only one gateway shows the uplink on its internal log, you need to move a gateway until you get two in range. Then you can watch the TTS gateway consoles. And then capture the meta-data.
Ideally you have two of this mystery device, one setup for ABP and one for OTAA. Plus some off the shelf devices setup for ABP and OTAA as well.
It seems deeply unlikely that it is firmware related, if the uplink is being processed OK by one gateway & getting through to the application console, it would be rather odd for it to be discarded by other gateways.
