Bug with my calculator

Hello everyone! Please tell me what is wrong with my calculator))? My calculator should pass test 9; It works normal, but when i press ‘run tests’ in freecodecamp tests script, it show me that my calculator logic is wrong, and i cant pass test 9!! Look yourself and you will see. First calculate this example:
3 + 5 * 6 - 2 / 4. It will be 11.5. When press ‘run tests’,write smth and press ‘equal’. It will will show infinity! Why it happens? Please help.https://codepen.io/MotyBoom/pen/qBZYQyW

In showDefault you should reset no only display value, but also all the state variables (currentValue, action, nextValue, result)