Whenever someone else joins one of my worlds, I automatically get their player skin and they get mine. When there are 4 or more people in the world, everyone gets the skin of the person who joined most recently. I don’t really know why this is happening, and it did happen in 1.14 as well, but you used to be able to fix it by going into settings and changing it back. I am using a Kindle Fire HD 10(2017). But some of my friends are using other tablets and laptops and it happens in their worlds too.