We had an issue with the selection returned by the ScrollableDatatable component not matching up with what was being displayed by the component.
Basicly the component would show three lines selected but the selection in the component contained only 2 items.
Since I couldnt figure out why this would do this in our application I tried out the test case using the component demo and I have found the exact same issue on your demo page.
Here is how to reproduce it with the demo :
1- Select the first three rows using ctrl + click
2- Click on "Show current selection" , 3 selections are shown
3- Refresh the page, the selection should still be highlighted
4- Deselect with ctrl+click the first row
5- Click "Show Current Selection", 2 selections are shown
6- Deselect the second row with ctrl + click
7- Select the first row with ctrl + click
8- Click "Show Current Selection", only one selection is returned while the table shows two as selected.
At first I figured it might be linked with the refresh, but it doesnt seem to be. There is another issue I was able to reproduce on the demo.
1- Ctrl+click select the first three rows
2- Show selection, it shows 3 selection
3- ctrl+click the first row to deselect it
4- Show selection, it still shows 3
I think the issue might occur when you only use ctrl+click to select items after the component was rendered.
For the second example if at any time you actually simply click on one line then you never have the problem again.
In our first case the problem occured after the refresh since we already had a multiple selection and immediatly used ctrl + click to modify our selection.