Metal replaced Cedar Shakes

Have a log cabin that was restored/rebuilt in mid 70's and roof was finished with cedar shakes - then an addition was built with cedar shakes as the roofing material - in mid 90's the cedar shakes were replaced with a metal roof (not well versed in what type - but the type that you paint). Both the cabin and the addition do not have attic's - the addition is a catherdral ceiling. Few year's after metal roof was installed - found that there was a moisture problem in the apex of the catherdral ceiling. Initially there were no ridge roof vents and we also found pin holes at the ridge where the two sides of the roof join. A ridge cap was installed - the pin hole were repaired and the roof painted - it still seems that there is a moisture problem from time to time - there are venting soffits on the bottom edges so there must be channels all the way up to the ridge. What could be causing this moisture. This is basically a vacation home that is not used but on weekends and is closed up otherwise. Thank you for any suggestions.