SharePoint 2019 does not honor title changes for people.
We have looked at our AD sync for people (says it runs and is successful) and changed our indexing schemes (may not even be related) without success. The AD synch job in SP is set to 5 minutes (the default). Unsure if it matters we've switched between scheduled crawls and continuous without any change.
What we expect is that when "Regional Director" is promoted to "Director" that the title shows the updated "Director" only title. What actually happens is that the page loads and the people web part is displaying the contact information and shows "Director" but within about 1 second is updated onscreen to the old "Regional Director" title.
It is clear that SharePoint KNOWS what the new title is and even uses it but some other call-back retrieves an old title and replaces the onscreen version with it.
Additionally if we add a new people web part and include a person with an updated title the person is added with the correct title. Publishing the page shows the correct title but if we revisit the page (closed-open/refresh) the title exhibits the above "replace" behavior on screen.
This behavior occurs on any page, new or existing.
Not being a true SP admin (I'm learning it all on the fly) I don't even know where to look (or if there even is a place) to see what's happening in the AD space with SP except for the not-very-informative internal SP logs.
EDIT: I've noticed that when I look at this persons "people page" in SharePoint I see that it gives them their old title both in their actual title field but also in the hierarchy showing managers and direct reports.