Whenever a classic skin is used with the slim arm option, it'll automatically change to wide on restart of the game. This only occurs with classic skin imports from files, not from the marketplace classic skins.
How to replicate the issue:
Load in a classic skin via file
Click on the slim option (Left Option)
Save the character by exiting the dressing room
Restart the game
On load up, you should see the skin loaded via file with wide arms.
Devices Tested on: iOS, Windows
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We're tracking this issue in MCPE-186591, so this ticket is being resolved and linked as a duplicate.
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