Why does Network port failed to detect with error "Detected Tx Unit Hang" ?

Issue

• 2 ports of 4 port NIC are not being detected.
• The dmesg logs igb driver hang msg.

igb 0000:07:00.0: Detected Tx Unit Hang
  Tx Queue             <0>
  TDH                  <0>
  TDT                  <1>
  next_to_use          <1>
  next_to_clean        <0>
buffer_info[next_to_clean]
  time_stamp           <10729ffef>
  next_to_watch        <ffff88082f285000>
  jiffies              <1072a0a6c>
  desc.status          <1f0000>
igb 0000:07:00.0: Detected Tx Unit Hang
  Tx Queue             <7>
  TDH                  <0>
  TDT                  <2>
  next_to_use          <2>
  next_to_clean        <0>
buffer_info[next_to_clean]
  time_stamp           <1072a017f>
  next_to_watch        <ffff881029143000>
  jiffies              <1072a0e54>
  desc.status          <a8000>

igb 0000:07:00.1: Detected Tx Unit Hang
  Tx Queue             <0>
  TDH                  <0>
  TDT                  <1>
  next_to_use          <1>
  next_to_clean        <0>
buffer_info[next_to_clean]
  time_stamp           <1072a0a7b>
  next_to_watch        <ffff880831cfc000>
  jiffies              <1072a123f>
  desc.status          <1f0000>
igb 0000:07:00.0: eth2: Reset adapter
igb 0000:07:00.1: Detected Tx Unit Hang
  Tx Queue             <0>
  TDH                  <0>
  TDT                  <1>
  next_to_use          <1>
  next_to_clean        <0>
buffer_info[next_to_clean]
  time_stamp           <1072a0a7b>
  next_to_watch        <ffff880831cfc000>
  jiffies              <1072a1627>
  desc.status          <1f0000>