Thankyou for your reply.
Have you seen this on direct play or direct streamed files?
To be honest i’m not really sure how to tell, i’ve had a read of the below link and I don’t know of the compatible codecs/bitrates/containers for my android device.
https://support.plex.tv/articles/200250387-streaming-media-direct-play-and-direct-stream/
A video file I encountered this issue with yesterday has the following details;
.mkv extension/container
I would assume this is compatible with the client, but i’m not really sure how to tell.