Button works but Slider doesn't

I am running Windows 7, Arduino 1.6.5 r5,  aREST 2.4.1, and aREST_ UI 1.1.1 with a NodeMCU 1.0.
Everything works fine with  rest.button(5)  but there is no (PWM) output on GPIO5 when substituting  rest.slider(5). I definitely can't light up the same LED I was controlling with the ON/OFF Buttons.
I do have the working slider on my PC monitor.
Do I need an update to something?