I think it is the same problem GyGabor was mentioning. If you touch the jump button or any part of the screen before the joystick it cause problem with the joystick because the condition “Cursor/touch is on Object” does not take in to account multi touch, only 1 touch at the time. In order to solve this, you need to check for “new touch” in case the joystick is the second touch (so it is new) but also keep the current condition in case the joy is the first touch.
You are going to need to use the OR and AND blocks to work around this.
I have updated my example on itch.io with the solution, take a look and see if it solves the problem for you.
GyGabor also shared a nice example for dual joystick, have a look:
Simple dual stick 360 shooter - #7 by GyGabor