Zooming into VFR charts would consistently show all parts of chart at same zoom view
What actually happened
Please see the screenshots in sequence below. As I zoomed in, you can see parts of the Compass rose disappear and a “seam” appears as if parts of the chart are overlapping each other.
At this zoom level, chart is intact, looks normal:
As I zoom in, the truncation appears, zooming out restores normal appearance. Truncation is persistent at the first zoom level it appears and at closer zoom levels.
This is by design. The map automatically switches to the TAC (Terminal Area Chart) when zooming in. The upper part of your display switches to the Boston TAC for additional detail at this zoom level and therefore changes appearance. It may look odd when you are looking exactly at the edge as you are doing now.