Hmm, assuming that you have enough knowledge with network hardware/setting.
So that this can be excluded.

Than I think you may have a hardware problem with your motherboard.
Could be the network, flash nand chip, or even the cpu.
But still hard to say what it really can be.

I do not know if you have some technical skills to do some measurements on the main board.
If so, than I give you some information about this.

If not, you should consider to let it repaired by some one who have the knowledge to repair it.

You may also sent the motherboard to me, if you want that than sent me or Toysoft a private message for the address.