In a forum post over at OCAU, Dino from GIGABYTE has posted a fix for the incompatibility issues concerning Corsair PSUs AX760i/AX860i and GIGABYTE Z87X-OC/OC Force. The issue typically presents itself as failure to boot up properly, or in rare cases sudden shutdown. According to Dino, both power supplies and boards conform to Intel 8 series design specifications. It appears to be a signaling compatibility issue between the motherboard and power supply that is causing booting issues. GIGABYTE has provided information on a confirmed fix. The fix involves the removal of a resistor that controls the OC Ignition sensor for "PSU On signal". What's more, GIGABYTE offers a service to apply the fix via RMA.
Although the fix would imply the OC or OC Force motherboard is at fault here; it is still unclear which part is causing this issue. Neither Corsair nor GIGABYTE is officially commenting on the subject. This issue seems to occur only with the mainstream AX line-up; the Corsair AX1200i power supply is fully compatible with both motherboards. So far, there has been no report of other brands or product lines with similar incompatibility issues.
Fix for Z87X-OC (left), and fix for Z87X-OC Force (right)