As per this SO issue:

https://stackoverflow.com/questions/47781059/c-sharp-mongodb-tries-to-convert-enumuint32-to-int32-and-crashes

Easy to reproduce in EnumSerializerUInt32Tests.cs by switching from

        private enum E : uint
        {
            A = 1,
            B = 2
        }

to

        private enum E : uint
        {
            A = uint.MaxValue,
            B = 2
        }

and running the contained tests.

Result: Exception: "Value was either too large or too small for an Int32."

The problem here is in the EnumSerializer which attempts a Convert.ToInt32 for a Uint32 and a Convert.ToInt64 for a Uint64.