Hello, the dimensions of the new charts you open should be the same as the last one that was opened (unless you had another one that remained opened after closing the last one, in which case it seems the new charts will have the dimensions of the one that is still opened).
Have you tried resizing the chart so they fully display, saving your platform as is and then relaunching it and tried again, to see if you then get fully opened charts every time you open a new one? If this doesn’t work you should probably send PRT a technical report through the help menu.