Contacts not getting imported, but can be added and updated with exact same details

Hi there,

We're having an issue where the API does not import a significant number of contacts and it's unclear as to why. It seems that the problematic contacts can be added or updated successfully when done individually, but when done in bulk there are either cryptic errors such as "Error: contact_fields.value", or no error and the contact is simply not imported.

I can provide logs of a recent import where this happens, but due to the personal data contained within, I cannot share them on this forum. Is there a better means to reach out to support for this kind of issue?

What I probably can share here is the Activity ID, which is 3675b3a0-ded7-11ed-9a65-fa163ec497be. 

{
    "items_total_count": 837,
    "items_completed_count": 500,
    "person_count": 279,
    "error_count": 259,
    "correctable_count": 3,
    "cannot_add_to_list_count": 0
}

The end result appears to be 282 contacts being imported. 

Can someone help us with this?

Ryan