This sounds like other recent posts where I explained the steps I follow when I encounter a stubborn setting issue. Maybe it is unique to my setup, but I doubt it, so I will state it again here.
If a setting change requires you to close and restart MC to take effect, you have to make sure you close all MC server instances too for the setting to "stick". Sometimes MC server will still be running even if you don't see it among the system tray icons, so be sure to go to Task Manager and kill any instances you see there. When you re-launch, your setting change should hold.
This scenario has been very consistent over the years... I forget to close out MC server, and the setting change I made is ignored. I then immediately redo the setting change following the steps above, and now it holds... very repeatable. It is a bit tedious to have to do this every time, but at least it accomplishes the task. This workflow should not be required IMO... maybe the JRiver team can address this.
Hopefully this helps with your issue.