Random single hold violations on Arria V design that doesn't push timing or util. ???

It can, but not if the DSP blocks are too far apart. It doesnt have much scope to move them. The easiest way to make life easier is put an extra register between the DSPs in the source code, it means the path wont be so long and quartus has much greater scope to move them. Alternatively, use regions to lock specific DSPs in certain areas.