You can probably avoid this issue by choosing a Mac Pro system definition when you’re configuring MultiBeast.
Building My $1,200 Hackintosh
Mike Rundle

My system had the same issue, and I figured out something I haven’t seen around yet.
Essentially the graphic driver depends on (and its workings are tied to) the OS version.
Forcing Clover’s OS version to the current version your web driver is made for (in my case 10.11.5) will not make the driver fail when it’s time to switch between low res (boot phase 1) and high res (starting the UI).

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