Hi Michael,
I understand that you're seeing some duplicates when adding podcast episodes to your Up Next queue. It sounds like you've already taken some great troubleshooting steps; I'd like to help you get this sorted out.
Based on what you've already tried, I think it would be a good idea to completely remove the Podcasts app from your device and then reinstall it. You can find more information on this process here:
I understand that you're seeing some duplicates when adding podcast episodes to your Up Next queue. It sounds like you've already taken some great troubleshooting steps; I'd like to help you get this sorted out.
Based on what you've already tried, I think it would be a good idea to completely remove the Podcasts app from your device and then reinstall it. You can find more information on this process here:
Delete built-in Apple apps on your iOS 11 device or Apple Watch - Apple Support
Cheers.