XF 2.2 Multiple 2FA emails sent for login renewal

[Mouth]

I user with 2FA active, and and both App and Email Verification selected, is saying they get 12 seperate emails all at the same time when their login needs renewal. Says it's not the first time it's occurred. I cannot see anyway to diagnose this. No email sending log available, etc. No error in ACP error log. Email sending via Amazon SES, no sending logs available via their console either.

What can I do to ensure it's not an XF issue? Unlikely to be recipients mail server or mailbox issue.