itunes duplicating tv episodes

I'm having a problem with my library on my Mac Mini mostly where the TV episodes often double up even though I've downloaded one it wants to download another so I either have to hide it which often means I can't see it on my other devices until I go into my account and unhide it but if I delete the original download then re-download this sorts it out but I don't want to keep re-downloading these episodes all the time. Is this a settings thing in my account or Mac I have looked but I can't see anything , does anyone else get this problem and have you managed to sort it out. I'm using ios 12.0.1 i believe on my mac that is 2012 thanks for any help.