The officer changing the court date (assuming he did so without proper notice) is not likely to cause a dismissal of your case, though it might be grounds to dismiss any penalties you might otherwise receive for failing to appear in court.
If MN prosecutes traffic offenses through the use of a prosecutor of some kind, you might want to bring the issue to that official. If not, then you might want to consider a complaint to the employing agency.
But, the issue may be considered two separate matters and unrelated to your guilt or innocence.
There might be someone more familiar with MN law in this regard, but even in my state where this is verboten, such a change would not necessarily invalidate the offense. However, here, there are ways to leverage that such that the offense could get dismissed ... I imagine that is the same there. Look up "demurrer" and how it might apply in MN law.