I would think your problem is due to water ingress at the joint on the pole. Did you ever tell any of the 6 engineers it happens when its raining? If it was dry when they attended any test they did would not show a problem.
Hi Pipincp
Yes!.. I explained to every engineer, every time i explained that its mainly when its raining and/or very windy. the last buy went up the pole and said it all looks fine.
Kind Regards
Mark