Hi. The option “Match the client resolution upon connecting” is stored in the connection file, so each time you create a new one it is set to default. You may distribute preconfigured connection files to your clients to disable the screen resolution change, or if you want to completely disable resize of physical desktops on a server, you may change the following key in the file server.cfg:
#
# Set the interaction level for the session connected to the physical
# desktop:
#
# 0: View-only. The session is connected to the desktop in
# view-only mode, i.e. the user can't interact with the
# physical desktop.
#
# 1: Restricted. User connected to the physical desktop can
# interact with the desktop except for resize operations.
#
# 2: Interactive. User connected to the physical desktop has
# full interaction with the desktop.
#
PhysicalDesktopMode 1