I just downloaded Landmark 2019 onto my Dell (Windows 10 Pro 2.6 GHz 64 bit)  When I create a new drawing and add lines or shapes and use the pan tool to move around, the screen begins to flash with sort of a negative image of the drawing.  The grid lines are surrounded by light strips and the area between the grids is dark.  I am just starting to play with 2019 but I have never seen anything like this.  I have been using 2016 and have Service Select.  Did not like 2017 and never downloaded 2018