Zero returned for that, I'll try it again if/when it plays up again.
I should note, I did swap the power supply with another of the same type when I switched the RasPi running PiHole in an effort to resolve the bug. Same problem, different hardware, different power adaptors, different physical locations (and therefore electrical rings). I doubt this is the issue but I'll check nontheless if the problem persists. Both adaptors are 5V3A.