I am experiencing the same problem with ACF Pro 5.5.0. At first a specific repeater showed no data anymore in the admin, recreating the repeater made the data visible again. Currently however, the data is visible in the admin but the frontend doesn’t show it anymore, it outputs the number of rows (meta_value) instead.
For instance, this is a repeater group in the database with two rows:
meta_id post_id meta_key meta_value
366 62 my_repeater 2
Calling this repeater from the frontend gives back the meta_value, instead of the actual rows:
$test = get_field('my_repeater');
print_r($test);
output: 2
