Potential Map Issue - Decay - Sections of Map Not Connected

Perhaps I'm missing some secret tunnel or something, but I've been wandering around on this map for about 15 minutes and I can't find a way to the other areas of the map. This appears to be a map generation issue unless I'm missing some secret mushroom I need to click or something (like the switches in the Crypt maps).

I had the exact same encounter, couldn't finish map :(