Chromecast can't play some files



I have a Synology disk with Plex server on. When I try some files it’s looks like it is starting the series in the app but then that screen disappear and the series don’t start.

Last time I downloaded a new series with donate and started to watch it and it worked fine but after like 30 I guess donate found a new version of the files and after that I can’t play it on chrome cast. So I think it have something to do with the processor in my Synology that can’t handle that file.

I can see in donate log that the file was swamped to another format look at attachment

So the question is should I tell somnar to never download x264 or HDTV or what should I not download?

Thanks in advance