Transmission

I am original owner of a 2003 honda pilot with 150k miles. When cornering or slowing down (not having come to a full stop), vehicle just shifts out of drive at around 1000-1100 rpm's. This happens only when rpm's are being reduced. When given gas to accelerate, engine just revs. When engine settles down to about 800 rpm's, I can resume acceleration, which is smooth through all the gears. No 'check engine' light comes on and therefore no codes. Tranny fluid is clean and red. I would like to have an idea of the problem before I take it for service. Thanks.