Trending Issue: SPSE – “The server tag is not well formed” on certain Search administration pages after March 2025 CU
After installing the March 2025 CU (or any subsequent update) for SharePoint Server Subscription Edition, certain search administration pages include incorrect ASP.NET tags leading to the following or similar error message: An error occurred during the processing of /_admin/search/listmanagedproperties.aspx. The server tag is not well formed. System.Web.HttpException (0x80004005): The server tag is not well formed. […]