No trailers play when I start a movie.
Settings are as here:
Cinema Mode is enabled in playback for 'movies' and 'episodes'.
I disabled all the internet based trailers since I have local versions.
I enabled 'include trailers from movies in my library'.
I set 'number of trailers' to '3'
I enabled 'only play trailers from unwatched content'.
emby is Version 18.104.22.168
this happens for me both in
the web interface,
the kodi app (I've got premium)
from kodi on the same machine as the emby-server,
from kodi on another machine.
My trailers are stored beside the movies in the same directory, like so: