@vervoortyves As stated in the documentation:
You cannot modify the data array in-place. To add, change, or remove objects from the repeater’s data array:
-
Store the value of the data property in a variable.
-
Make changes to the objects of the data array.
-
Reset the data property with the modified array.
Regarding your question about preview vs live: Preview and Live are currently rendered with different engines. Preview will eventually be rendered using the same engine as Live.