Watcher email remains (uneditable) in field

Hi all
Interesting issue:
I add a requestor (or any type of Watcher) to a ticket, no problems.
I remove said watcher and they disappear as expected, cease getting notifications, etc.
But when I go to the People tab of a ticket, I see that previous watcher listed, and cannot edit that field.
I can re-add them in that screen successfully but the same thing happens when I remove them again.
This happens on both privileged and unprivileged users.
Attached is screenshot of it. The two names cannot be edited.

I’m hopeful someone else has seen this and may know what the cause is?

I am using 5.0.1 on Ubuntu 18.04 with MySQL 5.7.34, and with the following plugins:
RT-Authen-OAuth2
RT-Extension-Announce
RT-Extension-CommandByMail
RT-Extension-CommentOnCreate
RT-Extension-CustomField-HideEmptyValues
RT-Extension-CustomFieldsOnUpdate
RT-Extension-ExcelFeed
RT-Extension-Gravatar
RT-Extension-HistoryFilter
RT-Extension-JSGantt
RT-Extension-Memo
RT-Extension-NotifyOwners
RT-Extension-TicketLocking
RT-Extension-TimeTracking
RT-Extension-TimeTracking-Automatic
RT-Extension-UserDetails

Note: I did disable all plugins (except OAuth2), removed var/mason_data/obj/* and restarted Apache, but could still replicate the problem.

Thanks!
Brent

Hmmm, Never mind!
I’m going to consider this a one-off, probably caused by solar flares or aliens =)
I’ve been testing (read: mucking about) with it some more and it seems to be isolated to this one ticket and just these two users.
Seriously odd but since it appears (so far!) to be isolated I’m not going to worry about it.

I believe RT is just adding some suggested users it saw in the ticket history