I was told about a similar situation. When your turning the machine, the system doesn't immediately recognize what your doing. So it will typically drag the blade in the direction your turning. Topcon has an extra processor that recognizes the turn faster than Trimble or Leica. I was told this by a Topcon guy so......I will say that my Topcon system does not dig in the corners. I have over simplified this but that is the general idea.