This error means your UpdateBillboard function has the wrong type of input. Since you didn’t include the function it’s tough to troubleshoot but it should look like UpdateBillboard(maybeAgent : ?agent): void = block: I recommend looking at the documentation about options to understand better. option docs
Seeing how many repetitive variables and functions you have, you are bound to have more errors down the line as well. In programming you want to always avoid repetition, I would recommend some good coding practice tutorials or maybe giving your code to an AI like Claude to optimize so you can see how this is done.
For example, instead of having a bunch of billboard devices, have an editable array of billboard devices, or an editable array of Billboard custom classes that stores the device and any other data you need. Same with the Trigger devices.
Do you need separate functions for each billboard or can you have one function to subscribe to that works for them all? Abstract functions can be useful if you need separate logic for each one.