Strange Bodyslide Effect with Leather Chestpiece

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I'm just curious about what causes this effect. This is taken from the Skimpy Armour and Clothing Replacer https://www.nexusmods.com/fallout4/mods/7718 (including the Vault Suit) and looks perfectly normal as you can see:

 

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But when I change the the Vault Suit for Raider Leathers based on Lazman's Armour Replacer https://www.nexusmods.com/fallout4/mods/20628 the chest piece seems to lose it's Bodyslide setting

 

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If I go back to the Vault Suit it fits again, so I was really curious as to what causes this as I have noticed it happen with a few other things as well (like underwear that fits by itself but grows with certain dresses)