That voltage does not make any sense. Forcing it to work with that amount of V is causing an underlying issue to get fixed. My bet is on the pll override finetuning, which on the GD65 was fixable with a small workaround (ineffective on UD7).
Also, I don't think the max of your chip is 4800. I don't think anyone's max is 4800. With my ES chip, I had this 4800 air wall on all boards I tested (GD65/UD7/DX79SI) and it could do 5300 on LN2 (Sabertooth/GD65/UD7) easily. On GD65 I got upto 5150 air after workaround fix. With this 3930K retail, I have a 4700/4800 air wall on the UD7, so far, but 5200 bootable on R4E. Actually, I got a similar wall before I started playing with PWM settings on the R4E ...