Please don't repost the same issue with a different name...
Check your driver code, from what the other user said, looks like non-IP
packets are being discarded without freeing their buffer.
Check with the one who wrote the driver and/or the port.
When the Ethernet controller signals frame(s) pending, the receiving
task allocates a buffer for it and transfers data. Then, this buffer is
checked for upper-layer protocol and handled to the stack or discarded.
Code for this is in the netif tree and is modified by the one providing
the driver and the port.