I downloaded the free version of PHP Grid to explore the possibilities. I am adding one by one customized columns and it seems to work fine. Until I add a column that contains some empty cells. Edits in rows that contain an empty cell aren't saved while edits in rows with no empty cell are still being saved correctly. Either changes of the empty cell to a value are saved.
I can't figure out why an empty value makes it impossible to make changes to the whole row. In this specific case it is essential that the specific column can also contain empty cells. I appreciate your help!