Trailers do not load when refreshing metadata

I’m having problems getting trailers to load for new movies added to the Plex server. This have worked previously but not anymore. I have used the Plex Movie Agent to get the trailers, and yes, I have a valid Plex pass. If I open an old movie it will contain a trailer, but if I refresh the metadata the trailer disappears… can anybody help?
For info; I have tried clearing the caches for the plug-ins. This did not help.
Thanks in advance