This is happening with me as well. A work around I found online for a similar problem that works is to add the podcast to a playlist then sync the playlist. The annoying thing though is the podcast playback doesn't pause during exercise notifications, it just lowers the volume like it does with music.
We have an open ticket for the media error that you are receiving when using Spotify. You will want to update the Spotify app through the ConnectIQ store to alleviate this disruption.
