I have enabled the possibility to select multiple rows in a TDBAdvGrid. PageMode is set to False. So far so good, but when you also want to sort the grid the selections are "scrambled".
I'm not sure, if that helps - but I had an issue with scrambled sorting in a TAdvStringGrid.
I had to explictely format the "problematic" row as ssAlphabetic. That solved the issue.
I don't know if this is useful for DBAdvGrids also...