Skin packs in split-screen unload as soon as we enter separate chunks, and do not load again.
Also, the skin for the secondary player is not saved, as this might be an issue with the switch account system, but I'm sure you could find a workaround
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Thank you for your report!
We're tracking this issue in MCPE-78206 and MCPE-58640, so this ticket is being resolved and linked as a duplicate.
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