When creating rules in guided editor, we are running into validation errors depending on the order of the conditions. The problem is that the order of the conditions is important:

when
  COND_X
  COND_Y   => works

when
  COND_Y
  COND_X   => fails

java.lang.AssertionError: [10,18]: [ERR 101] Line 10:18 no viable alternative at input 'Number' in rule "ATO_Negative_AU_Test"
[0,0]: Parser returned a null Package

Test cases showing the compilation failures (@Test testOrder1 vs
testOrder2) can be found here:
https://gist.github.com/martinweiler/e684a0e75a2c9f4de4dee5a13affb8b0