I have a redundant search topology with 2 search servers and 10 WFEs on top of SharePoint 2019, my web application is extended to Intranet zone, the reason the web application is extended is due to ADFS integration, so the Default zone has ADFS trusted identity provider only enabled, and the Intranet zone has NTLM authentication only enabled.
In AAM, we set the Default zone to web application URL, and in the Inranet zone we set it to the extended application URL, knowing that the Intranet zone URL is HTTP not HTTPS.
In content source I'm using the URL that exists in Intranet zone.
Once I start full crawl, it can crawl many items but many content pages (ASPX pages) inside my SharePoint site throw the error message below in crawl log:
"The SharePoint item being crawled returned an error when attempting to download the item (SearchID=xxxxxxx")"
Therefore those items that have the error above will not be crawled and will not be retrieved in the search result.
Any help would be appreciated.