Skin model reverts from slim to default after restarting the game.

When I import a custom skin and select the slim model, it looks fine when I'm on but , when I exit and reopen the game, the skin reverts to the default bulky model. I’ve tried reapplying the skin, but the issue persists after every restart. also it doesn't appear on the my owners skins tab. 

 

This happens consistently and seems to be an issue with the skin importer or model selection.