When adding a new field to a repeater that already has entries, the new field is not available to the prior entries. Adding this field to prior entries requires editing the JSON object of every entry to include this field in the field structure, which is problematic.
For example, let’s say I have collection A with a repeater. In collection A, I have entries that average 10-20 repeater values. To add the new field, I have to edit each entry’s JSON object and insert the repeater JSON 10-20 times (injecting the JSON structure of the field into the repeater’s fields’ structure).
As you can see, this is unsustainable.