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I have found that after the recent update, gear has random skins applied to it based on your items you have selected as favorites. I thought it was odd that my Memento backpack had one of the skins from the last apparel event instead of the Memento's original skin, and noticed that I had selected those skins as favorites. This also happened with the gloves I was wearing, except that it randomly chose the Firewall gloves skin, which I had not selected as favorite, but it overrode the skin that I actually had selected as favorite.
Once I unfavorited ( for lack of a better word) or deselected all items I had originally selected as favorite, all skins returned to their normal versions. I then selected the skin I wanted to override the gear ( without marking it as favorite) and everything looks normal.
TLDR: Marking any transmog skin as favorite will have it randomly override any gear you have currently transmogged with one of your favorite transmogs, or a random skin ( for gloves, etc..). Unmarking all skins from favorites fixes this issue, and you can then transmog to what you wanted, but if you mark as favorite, you will get a random skin.
This also applies to exotic gear pieces ( Memento, Ninja Bike, etc...) as even they will be overridden. I deselected all favorites and had the normal skin, then marked one of the new backpacks as favorite, and it overrode the Memento skin.
Edit: It doesn't seem to be related to favorites after all. It seems like the game is overriding all appearance transmogs on gearset items and exotic gear with apparel event items. If you have certain appearance items set on high-end ( Yellow/ Gold) gear pieces, you can reset them by choosing them again; however, it doesn't seem to work with named gearsets ( Green) or exotics- they all seem to get overridden. You can choose which apparel event skin it will appear as, but only apparel event skins.