Intel has identified the root cause of the recent reboot issues plaguing the company's 'Broadwell' and 'Haswell' chips that received a microcode update for the Meltdown and Spectre exploits. The company has issued an updated guidance for customers and partners in this regard.
https://www.notebookcheck.net/Intel-readying-a-more-reliable-Meltdown-Spectre-fix-for-Broadwell-and-Haswell-platforms.279860.0.html