I noticed this, when i accidentally forgot the "Set PWN" with Level=0 at the beginning of engine2 (which waits for a trigger from engine1). I wasn't able to test the pattern in the app, but the pattern was working anyway.

Similar issue, when i forgot the "Return to start" at the end of engine2: The pattern was working, but the app returned an error code.

Interrupts of testing were noticed, when engine1 is still on and engine2 comes in. when plugged to usb, testing is interrupted immediatelly.

Just noticed that sometimes testing is only possible, when edited before and clicked on done already (may because of manual edit).