I have had multiple projects where the UI seems to become "corrupt" in the designer. It always seems to pertain to split containers, DataGridViews, and anchoring the DGV inside the split container. It seems the DGV anchor somehow becomes de-synced and the DGV grows larger than the Panel that it is supposed to be anchored within. This causes a part of the DGV to be cut off and no scrollbar is available to see the rest.
Has anyone encountered this, and hopefully also found a fix?