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 lowered. When given gas to accelerate, engine just revs. When engine settles down to about 800 rpm, 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'd like to have an idea of the problem before I take it in for service. Thanks.