I'd be interested in knowing how you make out with this. We have a 2019 15XPC with the 4.3L PSI gas and that same style Murphy control panel. Back in January, at 720 hrs, it had a spell or two where it would not repond to any button input. None of the buttons on the control panel worked. It still started and ran, and you could still throttle up by pressing the button back by the infeed, but no way to throttle down unless Fuel Saver kicked in. Our mechanic checked the connectors that plugged into the back of the panel, and after working with those the issue went away and has not come back. However, it sounds to me like your issue is different, more of a physical wear or dirt issue.
FWIW, While we were troubleshooting, I did speak with a service tech at Winchester Equipment and his take was that these control panels are not serviceable, that they are sealed or fused together at the factory and they're near impossible to open up without destroying them. (But some of that may depend how badly you want it to work.)
For this machine, that Bandit part number was 300-8012-67 and between $850 and $900 in price.