Spirit System

When moving the throttle stick up and down during set up (using the green channel bars), as I move the stick channel 6 (pitch) moves smoothly but the throttle channel is sticky and not fluid.
I have changed the transmitter over and it does the same thing.
The transmitter is Frsky Teranis with a sbus XM plus and I have used a Radiomaster R81 receiver satellite, both show the same issue on the throttle channel.

Anyone any ideas

Spirit 2

I am not sure what do you mean by sticky, but if you are looking only at the Throttle bar it will not update fluently. Software is refreshing channel values with around 100 - 200ms rate. So you will see jumps there.
In any case it should be similar for each channel.

Is there any issue when flying?

HI it only is an issue on the throttle channel all the others are fine, I have not flown the heli as I really don't trust the system at the moment.

also the pitch channel works fine but there is no way for me to physically test the throttle channel. all the moment on the others is as expected.

You can connect a servo at the throttle port - where your ESC is now. In this way you can verify it works well.