I just found that it's all about the thunderbolt port that you're connecting.
I have 3 tb devices connecting my macbook pro 15" in total.
If I connect the akitio pcie box to the tb port that located next to the power port, I just can't boot into windows when I have it plugging into my mac. What I need to do is plug it out first and wait for my mac goes into the loading spinner than plug the tb cable back into my mac asap.
But if I plug my akitio to the tb port that next to the usb port and have my wd tb drive plug in to the tb port next to the power port, everything works fine and I can boot into windows 10 successfully for 100% of the time if I perform a cold start and around 50% of the time if I perform a reboot. fyr