Debug issue with popup-modal notices not loading

[maxinacube]

We have seen an issue arise where AJAX notices for the popup-modal location are not consistently being shown

We have seen occasionally that the request for the popup-modal isn't ever sent and have also seen the response for popup-modal come back with a 403 -- error is as follows:

{"code":"rest_cookie_invalid_nonce", "message":"Cookie check failed", "data":{"status":403}}

[maxinacube]

@aaronware It looks like we may have resolved the 403 at some point, not sure if it had been accidentally reverted or if this is creeping up because of a different reason. See PR #146

Just to reiterate, though, that the 403 is seen on a failed response, while another issue we've seen is the request not being sent at all