Error when creating group channel Invalid value: is_distinct

For only some attempts to create a group channel I am receiving the following error message
'Invalid value: "is_distinct. If you want this value to be set "true", user_ids must be required.".'

Can someone provide some details on what this error means? The user_ids we are sending correspond to active users and there is no existing channel with all of these users in it.

The same function succeeds for the majority of requests so I am not sure what is different about the ones that fail.