Hi Alice,
I knew finally the root cause, it looks very weird... Just FYI.
I pasted a .xlsx file in KDS project explorer so I can open it together with my codes in the same window, and this file may cause the issue. After I delete it, build is successful. I've repeated paste/delete actions for a few times and every times the same behavior.
I don't know why a .xlsx may cause this build issue and don't plan to deep dive into it. Just tell my finding.
Walter.