9560 Hackintosh restarts under full load

I was recently testing undervolting on my Hackintosh 9560 4K model. And I notice that when it was loading a website, opening FCPX or After effects (full load situation), the screen would turned black suddenly, and the system restarts. Which is kind of annoying, this meaning I’m always risking my work doing high load work like video editing. Anyway to fix that? Thanks in advance.