When a PDF file is opened from a mapped share e.g. N:\test.pdf which is mapped to a Windows 2022 DFS share e.g. \contoso.com\dfs\myshare\test.pdf. In Windows 11 when saving this file adobe reader prompts the message: "This document could not be saved. Cannot save to this filename. Please save the document with a different name or in a different folder". And the app suggests a temp folder on the computer with at temp file name. This issue only happens in Windows 11 and not in Windows 10. The issue has been tested with the same user account on both machines. The issue has been tested on multiple Windows 11 and Windows 10. All of the Windows 11's has the issue, while all Windows 10's works perfectly fine.
When using directly shares from the server e.g. \windows22.contoso.com\myshare\test.pdf there are no issue in both Windows 11 and Windows 10.