I had a points stay starting March 18th at a hotel that lowered category. I called soon after the stay and was told that the points adjustment would take up to a month to post. I called back today and they tried to claim I was ineligible because the stay began on March 18th instead of the 19th. Luckily, I had saved a copy of the terms:
"Any Free Night or Points & Cash Award booked prior to 11:01 p.m. CT, March 18, 2019, for nights on or after March 18, 2019, at a property that is shifting to a lower category and will require fewer points will receive an adjustment."
They relented and manually issued a credit. Disappointed that they didn't program the auto-credit exactly as the terms described.