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

Hold violations are cause by routes between registers being too long. To fix them, you make the distance between the reg's shorter. If this becomes too hard, because there are too many luts between the reg's, or the regs are inside the multiplers that cannot move, the easiest way to fix it is to add another stage in the pipeline between the multipliers to allow the fitter to shorten the distance between registers.