On my Xbox I equipped a skin from a skin pack and it says it's usable cross platform. On my phone I don't use skin packs I use the skin I made myself but upon startup my skin automatically changes to the one I have equipped on my Xbox even though Everytime I play mobile I equip my custom skin. I think it's the cross platform feature for skins which should be removed in my opinion
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Same problem on Windows 10 version. I have a custom skin and every time I start Minecraft, this skin is replaced by the last store-skin I've selected.