Good day,
It seems to be random, as other folks have stated. In this very specific case, it may very well be the items I have chosen for this outfit. The outfit I have saved to outfit slot "Outfit 1" looks completely fine in the Outfitter window.
This oddball outfit is in slot "Outfit 2"
Pieces I am using for the outfit:
[Remnant Arkanian Warrior's Headgear], dye module open
(currently equipped) [TT-17A Hydra Bracers]
[Corellian Battler Jacket], stamped dye (Secondary Deep Pink Dye Module)
[Remnant Dreadguard Trooper's Gauntlets], dye module open
[Mercenary's Boots], dye module open
[Remnant Dreadguard Trooper's Belt], dye module open
[Remnant Arkanian Trooper's Legplates], dye module open
2x [HK-55's Blaster Pistol], (Advanced Black-Yellow Fortitude Crystal)
It doesn't seem to matter in-which order I equip the pieces within the Outfitter window.
If I CTRL+Left-Click to preview these items instead, everything looks fine.
And, as-mentioned originally, things look fine in-world.
Hope this information is useful.
Best Regards