I tried the later proposition and it didn’t work.
But I’ve to say, it’s quite complicated and it’s possible I made one or more mistake by copying. Than I had to copy back my saved files (don’t forget to do it before trying this solution).
Does someone else made a better experience than mine?
I’ve approximatively the same problem. The alert on WP is:
Warning: Declaration of WOWSlider_List_Table::single_row($id, $data, $index) should be compatible with WP_List_Table::single_row($item) in /volume2/web/mybees/wp-content/plugins/wowslider/list-table.php on line 0