I was driving from Volos to Mouresi, Pelion peninsula, crossing it from west to east.
By the time I came to the turn to Katochori, before the village of Portaria, Waze instructed me to turn to Katochori rather than continue through Portaria. It turns out that the way through Katochori is very dangerous: part of the road is very narrow and part is very very steep! So I had to go back to the beginning and continue my way through Portaria. In conversation with an Israeli I met later on, it turns out that he and others experienced the same problem.
I would suggest that you bring this issue to the Greek forums so that people with access to that area can edit the map to try to avoid this routing.
Also provide a permalink to the area if possible.
Sorry to hear that addish.
I went through the area you describe and i think i found the “problematic” segments. They didn’t have asphalt but concrete, correct? Do provide a permalink just to be on the safe side 
I marked one of the segments as a dirt road so no other Wazers are routed through there to save time and everyone uses the Primary Street despite the shorter route that goes through the street.
However, i’d like to fully echo vince’s comment. Do post relevant issues in the Greek subforum to be sure we will address it.
Btw, if any global mods see this, pls do move it there. kthxbai.
Moved