Yeah, although I think the problem is somewhere else. You might have an undervoltage-induced error only because of one of the frequencies. So not all the voltage settings, just a particular one.
And only that one is giving you trouble. It was like that with my Z5C. Ofc, if you get more reboots then either your voltage for the problematic freq is too low or you have several problematic frequencies.
Apart from that, my Z5C is pretty stable. So if there is an error, it's from a race condition somewhere that's exacerbated from the inaccurate voltage tweaks.
I think I tried setting all voltages individually, as GreyLeshy posted in a screenshot few posts back, but something made me unable to set it exactly like that, after changing a specific one, it automatically changed another. I will give it another try to explain this better.