I think the oncomplete attribute doesn't have any sense here (why showing the modalpanel if modalpanel is already opened?)
Ok, I placed the oncomplete attribute as a workaround to keep the modalPanel from being closed. If I remove that attribute, when user selects any row in scrollableDataTable, modalPanel is getting closed.
remove your oncomplete and try to add just limittolist="true" to the support.
I guess your modal lies in some autoupdatable outputPanel or include. So closure in this case occurs by design.
That worked. Thank you very much. Yes, my modalPanel is in included page in a tab.