My experience has been the resin buildup on the tools. When I have
turned really green or wet woods, the heat seems to dry out (cook?)
the resin from the sap onto the tools. Just like a saw blade, a resin
encrusted cutting tool is its own worst enemy because as the resin
builds, it generates more heat. As the heat rises it cooks more resin
onto the cutting edge.

I always keep a large cup of water next to the grinder, and when I
turn really wet woods I dip the tool into water and wipe before
getting resin into/onto my grinding wheels.

Robert