Typical situation when a server error may occur is exceeding the allowed server permissions.
For example: the system creates and saves a page with the 0777 permissions, while the maximum permission allowed by the server is 0644. The server will return the 500 error upon attempt to access the page.
To eliminate this error ensure that the server allows to access files whose CHMOD attributes are 0777.
For Bitrix Site Manager, add the following lines to the dbconn.php file:
Instead of 0777, you can use values allowed by the server for files and folders, respectively. The following values are usually sufficient: