I have a datagrid with frozen columns at the start. Above the grid I have some OutsystemsUI Advanced\DropdownServerSide widgets.

The balloon of the drop-down falls underneath the data grid header when some columns are frozen.

This seem to be caused by the z-index on the [wj-part="ch"] div element. For some reason the z-index changes from z-index 3 when no columns are frozen to z-index 5 when some columns are frozen. The balloon of the drop-down has a z-index of 5 too which is causing this issue. Manually setting the z-index back to 3 solves the issue, as far I can see without problem with the datagrid. 

However I don't have control of this element of the data grid. Because the z-index is directly on the element I can only overrule the z-index with an !important tag, which is not preferable.

For now I increased the z-index of the drop-down by changing the Outsystems theme CSS variable --layer-system-scale from 5 to 10. This gives the drop-down balloon a higher z-index and solving the issue.

:root {  --layer-system-scale: 10; }

Although I solved the issue with this solution, I would wonder if it could be fixed from the datagrid widget so we don't have to change the OutsystemsUI theme variable (which might cause other issues).

In the image below you can see the issue