I am also having problems with Banana Pi r2 v1. when it comes to have high loads on multiple interfaces. Example: If there is only forward traffic from wan to lan0 interface (or vice-versa) no problems are note, but if during this traffic I start another traffic, by example, going out from lan1 interface, the output traffic simply does not work.
All these tests were made by using iperf and scp on OpenWrt 18.06.1, r7258-5eb055306f initramfs kernel.
I also compiled the entire openwrt trunk version and the result was the same even making some changes on gmac code on the dts file referenced in this thread but again, no solution.
Well, have we some news on this thread?