I have this same bit and use it allot on just this application. Seems that your blades pertrude beyone the roller or your roller is too small in diameter.
This definately should not occur. When all working right, this does it with one pass, of course depending on the amount of overhang.
Try using masking tape or blue tape on the area only where the roller rolls, this will shim the roller out a bit and allow for a scrape free area.
Just a thought.
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