If the device fails to resume at the last playback position and if changing playback position with the progress bar or the skip button fails, it means that the device built-in player doesn't fully support the file encoding.
Since v4.6, Podcast Addict allows you to choose another player engine called 'ExoPlayer'.
To do this, please go into Settings/Player/Audio then press on Player Engine. You can also customize the player by podcast.