Got the repaired board back from Colorado, took a little longer than expected, but it's running fine, and their service was informative and helpful the entire time.

Arrived at Bitmain warranty: Feb 23
Returned repaired: Mar 8
Cost $175 + $25 return shipping + $25 outbound shipping to CO

Have another dead R4 board to send, but you can't keep running the other half if you send one in like you can on the S9 (downclocked to 500 to keep the temp stable) Too much of the air pressure escapes on the open side. I suppose that space could be filled with something fire retardant to make it work, but I haven't figured that out yet.

So I either wait until another R4 board dies, so I can send in two at once. Or I send it in and power down the other board until it's fixed.

I think I'll wait and see. But at least we have a repair service in the states that works.