For now Greenify and 360 Security app have been identified as killing the app playback service way too often.
In that case make sure to disable those settings/apps in order to fix the issue.
If you're using a Samsung device, make sure that Podcast Addict isn't is the list of 'Optimized' apps. Optimized apps seems to be killed every xx minutes when in the background.
You'll find some screenshot and information here.