Player model changes between log-in while using a classic skin

I recently made a new player skin (via a pixel art application) and downloaded it for use on Minecraft Bedrock Edition on my Samsung tablet. I selected the classic player model for the skin, which is the one I feel best represents the character I based the skin on, but when I closed and reopened the application, the character model changed to the slim one. I'm not sure why, but I'm having to manually reupload the skin and reselect the wider character model every time this happens to fix it, as the skin is not added to my library upon upload like it would be on Java. I'm finding it very frustrating. I tried updating the game to see if that would stop this from happening because I'd been playing on 1.21.61 previously, but it still occurs most of the time when I sign back in. Might be related to the skins the game randomly assigns the player before the user signs in on the home menu screen? However it happens, it's pretty annoying.