Anders and I opened the HV cover in ITE and did  a visual check inside ITE HV  cover and top of TM3.Bill was with us and took the pictures. There was nothing obviously wrong when we opened the HV cover in ITE. We disconnected TM3 high current cables from ITE. Then we did an electrical check on TM3.The TM3 was good and passed megga test (465Mohm at 500V). The module was good and was separated electrically from the ITE at that moment. Then, we went back to electrical room and measured the resistance between bias and ground with ground bar opened and power supply disconnect. It was still shorted at that moment .We thought the short is located inside HV chase between electrical room and ITE. Then, we went back to ITE again and reconnected TM3 back to ITE. We wiped two blue nylon insulators between bias and ground, and no obviously spark track or dirty on them. We put HV cover back in ITE locked area, and went back to electrical room again.We decided to do a final electrical check there. We thought the short should be still there and we just want to confirm it . But this time the short  is gone. Everything goes back to normal.   The short disappeared and We test bias to 5KV and the current looks normal now.