Snorkel ATB-50 idle up issue

I have a 2000 Snorkel ATB-50 with a Ford propane engine. When I use the functions right after a start up, they idle the engine up just fine and work as they should. Once I go back to the foot pedal any try to use any functions, the idle won’t come up to higher idle to overcome the load so if I keep pushing the switch it will bog the engine and eventually kill it. I can sometimes get the idle to come up if I keep nudging the travel joystick a couple times but that doesn’t always work. If I shut the engine off and restart it, then it works fine the first time I use the foot switch and operation.
What component do I need to investigate or replace to get this idle up to react timely to the operational switches/joystick?

Thanks in advance.