I just had this happen to me on my five year old FEC-100 today. The other day I saw smoke coming out of the hopper, but it quit as the temperature got up to the 250 mark so I didn't think much about it. Today I did a 4.5 hour rib cook, forgot to turn it off so it went into hold mode for a little over three hours. When I remembered to turn it off I opened the hopper to see what was left of my pellets and there was quite a bit of water condensation on both the inside top lid, and sides of my hopper. Also more ash than normal inside the cooker.
We've had a ton of rain recently, but my FEC-100 lives under a covered patio with the cover on most of the time. No condensation in my hopper before the cook.