I have an Oregon 400t. I have noticed problems with Lake Pend Oreille. Some of the lake area just south of Sandpoint is missing. I think that the ground cover is overriding the water. Please note: Some of the map data may be based upon maps which were created before the construction of Albeni Falls Dam. The dam was constructed around 50 years ago. Many shallow areas of the lake and the Pend Oreille River have been covered with water since the dam was constructed. Possibly the ground cover data was taken from maps which were pre Albeni Falls Dam.
I have noticed that if I turn off the ground cover on the Oregon, this problem goes away.