I took a look at the code GusGameDev made, and I sort of understood it, but not enough to figure out what was wrong. So, I decided to make my own touchscreen joystick from scratch, getting most of the code done before I left for vacation. After a minor amount of tweaking/editing while here on vacation, I have a working touch screen joystick.
I can confirm the code works on iOS with multiple joysticks updating/working at the same time!
@JokerDDZ, I have sent you a private message with the project. I will make a tutorial explaining the code at some point in the future. (Sometime after I am back from vacation :sunglasses: ).