sorry for the delay, I was Trying by myself to resolve this, also with listbox and selectionCell, having the same result.
Yes, I have a ValueProvider for each ColumnConfig to get the value for the column in this specific row. I noticed that the problem is not the comboboxCell, but is in the PagingToolBar, that load the grid 2 times, and the second time I lost the values in the combo, the same happens when I refresh the pagingToolbar (loss of the selected values in the combo).
Instead when I load the grid without the pagingToolbar everything is ok.
Am I missing something, any suggestion?