What I have at the start:
1-Doctor_20Who_20-_20S03E04_20_28021_29_20-_20The_20Daleks_27_20Master_20Plan_20_2801_29_20-_20The_20Nightmare_20Begins_20_28Recon_29 Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2801_29 - The Nightmare Begins _28Recon_29
2-Doctor_20Who_20-_20S03E04_20_28021_29_20-_20The_20Daleks_27_20Master_20Plan_20_2802_29_20-_20Day_20of_20Armageddon Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2802_29 - Day of Armageddon
3-Doctor_20Who_20-_20S03E04_20_28021_29_20-_20The_20Daleks_27_20Master_20Plan_20_2803_29_20-_20Devil_27s_20Planet_20_28Recon_29 Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2803_29 - Devil_27s Planet _28Recon_29
4-Doctor_20Who_20-_20S03E04_20_28021_29_20-_20The_20Daleks_27_20Master_20Plan_20_2804_29_20-_20The_20Traitors_20_28Recon_29 Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2804_29 - The Traitors _28Recon_29
5-Doctor_20Who_20-_20S03E04_20_28021_29_20-_20The_20Daleks_27_20Master_20Plan_20_2805_29_20-_20Counter_20Plot Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2805_29 - Counter Plot
What I want (remove the _20 and replace them by SPACE)
1-Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2801_29 - The Nightmare Begins _28Recon_29
2-Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2802_29 - Day of Armageddon
3-Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2803_29 - Devil_27s Planet _28Recon_29
4-Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2804_29 - The Traitors _28Recon_29
5-Doctor Who - S03E04 _28021_29 - The Daleks_27 Master Plan _2805_29 - Counter Plot
this is the error I got

I'm prety sure the probleme come from the fact the the file name is too long but i'm not sure