I have 10 of them since something like 5 months. 2 hashing boards are dead from 2 different R4 so I mixed the 2 remaining working boards to make 1 complete R4.
6 controller boards also dead from electrical shutdown. I purchased some replacement S9 controller boards from Bitmain, reflashed them with R4 firmware and it works good.
Last week we had high winds and small tornados (really rare here), some tree broke and then we had an electrical shutdown, and 2 more controller boards died. I had only 1 replacement boards in hands so I connected 1 hashing board on an other R4, and the other hashing board also to an other R4. Original wires are long enough without modification. So I have 2 controller boards that control each 3x R4 hashing boards. Works really good. You have to keep the broken controller board plugued for the fan so your hashing boards doesnt fry.
R4 are not reliable at all and it doesnt worth it to send them to warranty. But... we already made profit on them even with a lot of dead boards so we don't really care if they die now.