We have notified the FAA about a georeferencing error on the latest Detroit Terminal Area Chart (Edition 78). When zoomed into the Detroit TAC inside ForeFlight Mobile, your aircraft position will not perfectly align with the underlying chart. This is most noticeable along the western edge of the TAC.
Please note that this does not impact the the Detroit sectional, which correctly shows aircraft position. You can see the Detroit sectional inside ForeFlight Mobile by zooming out in the Detroit area.