The issue is that I'm trying to create a Repeater field which has a single Text field within it. However, after clicking on update, the field is moved out of the Repeater field and placed as its neighbour. Researching, I only came up with issues where the field wasn't being saved at all, or the combined option names were too long if there was too much nesting of fields. I did increase the max_input_vars from the default 1000 to 3000, but nothing changes.
Adding a new sub-field within the repeater
The state of the field group after updating
Some other info that might prove to be useful:
- WordPress version: 5.0.3
- ACF version: 5.6.3
- PHP version: 5.6
EDIT: To answer the comment below, and for future reference if you can't view the images, the Field Names are landing_subtitles and subtitle for the Repater field and Text sub-field, respectively.