Cedar shingles in the Caribbean

Anyone out there have cedar shingle experience in the Caribbean, either Jamaica or Bahamas? Am just back and have observed some early failures with re-roofing required after 10-13 years…actually mildew or fungi growth starts at 5 years, splitting and curling between 8-10 years…rip off and replace 10-13 years.

Trying to figure out why?

Are these cedars laid over a solid deck?
If so is there cedar breather in there?
Are these shakes or cedar shingles?

Good question…they are open vaulted ceilings, loads of natural ventilation…Jamaicains in particular like to look up and see the natural cedar…so, roofs internally and externally open to the naked eye…occassional splitting thru the roof and radical buckling observed

Oooops an add on,no decks, just horizontal battens which are open mostly…no breather.

Ooops again…they are shingles, mostly untreated 18" Perfections, about 5.5" exposure…I have been in the roofing business 30 odd years in NA and Europe…seen nothing like it.