If you forgot to fix DataSource property on a grid,...

... although its child controls are set up properly, then your form may behave in a weird way.

For example, we have a form with 2 linked datasources (SalesTable and SalesLine) and 2 grids accordingly:

The second grid, SalesLineGrid, has DataSource property set to SalesTable. That value was set by default at the moment the grid control was created. You can also see 3 controls in the SalesLineGrid, but their DataSource properties are set to SalesLine, so they are fine.

Now, if we open the form and switch between sales orders back and forth, the bottom grid with sales order lines will not work properly:

As you can see, the cursor position in the second grid changes in sync with that of the first grid, there are a lot of "empty" sales order lines, and, finally, the rendered sales order lines are actually wrong.

Going back to the form in the AOT and setting the SaleLineGrid datasource property to SalesLine will fix the issue: