If bad packets are received at link partner, but no errors are seen during long
idle sequences, this can point to malformed packets on the TX AXI interface input.
Check whether packets are not being underrun. An explicit underrun is issued by
asserting tx_axis_tuser High while tx_axis_tlast is
High. An implicit underrun causes a frame transfer to be aborted when the tx_axis_tvalid is deasserted without asserting
tx_axis_tlast. Underrun packets will be transmitted with a block of errors
(0xFE).