As it's bought from other user which haven't been online for over a month i can't get Order ID which i need to send it back to Bitmain. Will wait until Bitmain warranty starts accepting reapirs of L3+ then send to them(they said after few weeks).
You can send the boards back to Bitmain and the out of warranty repair cost from Bitmain is not bad. The bad part is the time it takes for it to finally get to the repair facility, the repair to get done, and then get the boards back to you.
The average I would say is 1-1.5 months total to get a board repair completed. The cost per board repair for the last ones I sent in were $35 per hash board. So the cost itself isn't bad. It is the time and opportunity cost that is the killer. At least with these miners you can send in just a bad board. The S9/T9/R4 you have to send the entire miner back and that is killer.
If you are in the US you can send to the US address and that dramatically reduces the shipping cost, but it doesn't speed up the time at all for the repair. Don't waste your money sending overnight or express mail or anything because once it gets to that address it is all slow boat to China from there.
Bitmain Warranty would turn it around much faster, but of course you pay a lot more to get the work done.