Correct. A dial is stateless.
You can also just rotate an image according to a value and use nil as the dial image.

A dial has no position, it just does left and right like an encoder. You would need to use the circular slider for that.

And what type of approach are you flying?

Are you using RealityXP?

Arduino's are not capable of doing this. A Raspberry Pi with Air Player could.

Air Player is only useful when you want to run instruments on multiple devices simultaneously. Or if the instrument PC isn't easy accessible, when it is behind a panel for example.

The log didn't show it closing, that's a bit weird. Maybe something crashed.

Please see our wiki:
https://siminnovations.com/wiki/index.p ... n_problems

No you don't need Air Player.

I don't know the syntax by memory, I will have to check on Wednesday. In your copy paste there's a { missing. I cannot see if this in your script file.