I have the same problem. I have a repeater inside a group. I can’t add new rows to the repeater, programatically. I have tried using add_row with field names or keys. add_row returns integers but in the backend I can’t see any values.
I have tested also with a repeater outside the group. On that it works using add_row.
Thanks for any help!
add_row(
"field_5b606d31f4bb9",
array(
"field_5b607763dc795" => 100,
"field_5b606d3bf4bba" => "10.10.2018"
),
$post->ID
);