Dear EHX staffs, thank you for the kind replies.
Today I noticed that if I set the pedal behavior with the Exp mode ON, then change another parameter (e.g. SHIFT 1) and operate the pedal without pressing the Exp button again, the malfunction occurs. If I press the Exp button before operating the pedal, it seems to work fine. Maybe is it necessary that the Exp button be lit when using the pedal?