Scenario: If the appliance is upgraded from 9.1R8.1 or before to 9.1R9 or later, we can experience the change in default behavior.
By default, Desktop background and Font Smoothing are disabled for any Windows Terminal Session.
Before 9.1R8.1 version, the desktop background was getting enabled by default only in windows 10. Enabling desktop background by default was an unexpected behavior which occurred only in Windows 10 OS and was considered a bug. This was happening due to certain changes in MSTSC experience settings in Windows 10 OS and this bug was fixed in version 9.1R8.2.