Woodburner installed through a metal roof

I have a zinc roof, it is only a 10 degree pitch. Excuse my lack of correct terminology from the beginning.
Just moved in new build. We had a 4.5 month delay moving in because of a leaking metal roof. Recently have had the roof repaired by the builders so just moved in. Builders suspected it was condensation issues.
I had a surveyor around from a very reputable Woodburner company who said they had experience and had fit many woodburners through metal roofs.
They were aware there was a problem with the roof as the fitting was delayed several months until it was fixed.
Anyhow, Woodburner now in, they cut straight through the metal roof and it has leaked badly every time it rains. They have now refit all around the external flue again and we are now waiting to see if it leaks again.
Any advise would be much appreciated. If it is condensation under the zinc roof dripping down the internal flue how can that be rectified?
Thanks look forward to hearing from you.