You sir, are my hero. I wasted about an hour trying to figure out what I was doing wrong.
And yes, they should REALLY add it to the docs.
This is only available in version 5.3.2, which I think has not yet been released.
I’m having the issue as well.
I’m having the same issue…sorta. I have the following field defined:

Through code, I am filling out the values of the repeater like so:
$emergency_contact = array('emergency_contact_full_name' => $EMERGENCY_CONTACT_FULL_NAME,
'emergency_contact_relationship_to_you' => $EMERGENCY_CONTACT_RELATIONSHIP,
'emergency_contact_phone' => $EMERGENCY_CONTACT_CONTACT_PHONE
);
update_field('volunteer_emergency_contact', $emergency_contact, $theId);
No errors when that code runs.
But when I try to load the CPT entry, WordPress just hangs and nothing happens. If I remove that line where the code gets updated, everything works just fine.
Am I supposed to create something to update the row in the repeater beforehand? Am a bit confused.
Thanks in advance!