If the playback stutters when you turn the screen off, it might be related to some Battery saver apps or settings.
Please make sure your device Battery saver mode is turned off, because it might lower the CPU speed and apps priority too much when the screen if off.
If you're using battery saver apps, please make sure to authorize Podcast Addict or disable those apps.
You should also exclude Podcast Addict from the device Optimzed Apps list.