Nicehash is releasing a new Nvidia miner capable of 50-60Sol/s and they are having issues with the risers also. Sources for this?
I think the riser issue was resolved. The duplicate check was moved from the host code to the gpu to reduce the bandwidth.
More info on the new nvidia miner:
https://forum.z.cash/t/nvidia-gtx-970-50-sol-s/7848