I searched and didn't see this covered before although I thought I saw a post about it.
My trailer sort order is reverse alphabetical even though I changed it to descending release date. I thought maybe Y-Trailers was the issue so I uninstalled then a Library Scan triggered (May be on a schedule of maybe triggered by uninstalling Y-Trailers)
At any rate, the sort order is still not what I expect to see.
Trailer Sorting.JPG 13.98KB 5 downloads
Actual Trailer Order.JPG 66.79KB 4 downloads
Emby Server Log 20190211.txt 13.59MB 1 downloads