Hi @ldq
This issue can occur when a previous value for ‘field_name’ existed with a value of 121. Perhaps this field used to be an image, file, or post object field?
I would set a max rows to 1. This will prevent the interface from rendering all the rows. Then save the repeater field with only 1 row. Now go back and remove the max rows limit from the field, and you should be good to go!
Thanks
E