Duplicate Podcasts

I use iTunes 12.2.1.16. There are 12 podcast abonnements active.

One of the abos (SWR3 Die größten Hits und ihre Geschichte) has a problem:

For some of the podcasts -not for all- itunes shows duplicate entries. In windows the filename ends with ...1.mp3 or ...2.mp3 and so so. Some of the podcasts have 4 or 5 files.

How can I stop that ?