brian3180,
There is a great thread under projects or attachments about road work with a box blade (BB)--it is several years old, but it helped me tremendously. I did a quick search but could not find it
There could be a couple of things going on. First, you most likely need to lengthen the top link for the BB to reduce the aggressiveness of the blades as the engage the ground. Since you are not trying to "scoop up" material, you want the top link long enough that the blades are no longer cutting.
Second, because the sides of a BB are short, it was very susceptible to the bumps and unevenness of the road the tractor wheels are going over. If the front wheels of the tractor start to go up a bump or a rise, the BB will dig in more aggressively as it flexes at the hitch. You need to look at the areas before and after the low spots to see if the road rises around them. To help mitigate this problem, raise the BB up so it is not in contact with the ground when you are in that part of the road--you will also need to make multiple passes.
Third, Raise the BB all the way up to dump the material you collected. Drop the BB and then go in reverse to to push the material, using the BB, into the low spots.
You did not mention the type of material you are working with...most of the time, you do need to break the material in the problem area with the rippers before you add new material, otherwise the problem will quickly reappear.
We do love to spend other people's money, but I have 3/4 of road to maintain and the best implement I bought was a dual beveled box blade--also called a land plane. Made road work significantly easier.
I'm at a lost as to why this is happening. It seems obvious on a few areas of my driveway that dip and look low. I can have a full box of skimmed driveway material and when I go through these supposed low areas the box blade digs and accumulates more material. I'm expecting for the box to empty onto these low spots but the opposite is happening. Right now I just know what I THINK I am doing right. I don't really know what I am doing wrong. I have a few ideas that seem obvious as to why this is happening but in my mind I feel that gravity is not doing its part. I can't get past that. 
