Could be a head gasket which is failing
You are correct, although SMOD is technically possible for any automatic trans with a radiator cooled trans cooler. Its just not common. Certain Toyota's and Honda's I have heard of with SMOD - just not very often.SMOD isn't an issue on that year, unless someone swapped in an old model radiator.
i flushed it twice and it seems like it is still there.Might be that there was a failure (transmission was replaced) that causes mixing of fluids, the problem was repaired but even after replacing all fluids there is still residual crap left over?