I have 5x RX480 (Saphhire Nitro +) with Blockchain drivers and custom BIOS. I'm limited to 1000W power. I'm currently mining ETH + LBRY but I have some wierd errors. GPU stops every few minutes and then starts again... I tryed lowering dcri but no help.
Your rig might drain up to 1000W during load and PSU fails to deliver the necessary current to GPUs. Get a wattmeter and check your real power consumption.