Update - We confirm that the backfill process has been completed for old messages, and now all the affected profiles reflect the information as expected.
Further, we will continue to monitor the system and provide another update when we have more information.
Nov 12, 16:45 CST

Update - We want to provide an update below;
Facebook Public Messages: Khoros provided a workaround that resolved the issue for public messages, and the user/author name started appearing as usual, but the profile pic is still not visible, for which the Khoros engineering team is partnering with the Facebook contact.
Facebook Private Messages: Author profile data (picture, info, name, etc.) is missing for Facebook private messages in Marketing due to a known issue at the Facebook end.
Facebook Page for reference: https://status.fb.com/graph-api

We are actively tracking the issue, and we will keep you updated on the progress when we have more information.
Nov 10, 12:44 CST

Update - We are closely monitoring the situation, and we will keep you updated on further progress.
Nov 10, 06:17 CST

Update - We have put a workaround and confirm that newly ingested messages appear with username now as usual, and you would still see old messages with "Unknown" username.
Further, we are working to reflect the username for old messages, and we will keep you posted on the progress.
Nov 9, 13:33 CST

Update - We are observing this behavior due to a known issue at the Facebook end and tracking the bug reported on the Facebook page.
We will keep you updated on the progress when we have more information from Facebook.
Bug link:
https://developers.facebook.com/support/bugs/371769324552375/
Nov 9, 08:49 CST

Update - We are actively investigating the issue, and we will keep you updated on the progress.
Nov 9, 05:25 CST

Update - We continue to investigate the issue, and we will keep you updated on the progress when we have more info.
Nov 9, 04:17 CST