It appears that in some case the layout of table columns are not properly layed out. This appears even more clearly when using column grouping where the group column does not align correctly with its contained columns.
Also the grid of the table is not aligned properly with the column boundaries.

See attached screenshot.

Note: in this case, the TableView's columnResizePolicy was set to TableView.CONSTRAINED_RESIZE_POLICY and no particular min, pref of max width were set to each TableColumn.