Upgrade from 11.5 to 12.0 , About page, external links and site_page_type_id

[ccto]

Hello Parallels,

We have upgraded one of Web Presence Builder standalone installation from 11.5.13 to 12.0.7

We found that a few content pages (less than 1% of record count), the content page "loss", and becomes external link logo inside Editor Pages.
(One of this site is our testing website, so we found it)

We tried to look at the database.

We found that for that testing site,
In the table - site_page
We use parent_id to search
Most of the pages site_page.site_page_type_id are 1, except that particular problematic page (site_page_type_id is 2)

We restored the original 11.5 database (before upgrade one), look at the same record, site_page_type_id was 2 already.
We wonder, under unknown circumstance inside 11.5, the editor will save the page with site_page_type_id = 2

(As I know there are no External link option in 11.5, right?)

If I manually change site_page_type_id from 2 to 1, apparently, that page "was recovered"

May Parallels kindly have a search?

I attached the 2 images for reference.

Thank you very much for your kind attention.

Regards
George