I have been working on tracking down what I believe to be the same problem. I have been working on a Variscite development kit with an iMX6 board and have a good test setup that I can somewhat regularly create the failure. The interesting thing is that I thought I was dropping packets but in actuality the packets are getting to the receive side but as malformed packets. Even more interesting is that the malformed packet is always the same and that it contains the following ASCII text in its payload: "Copyright (C) 2007-2013 Freescale Semiconductor, Inc. All Rights Reserved".
I am using iperf3 to send data from the iMX6 board to my desktop PC. See the link to my forum post on Variscite's wiki below. Note: I've also verified this issue exists on an iMX7 based board.