Skin reverts to previously equipped skin when equipping certain skins from skin packs

When I equip a skin from a skin pack that I’ve upload to minecraft from an app or a website it unequips the skin and changes it to one from the minecart character creator.

Steps to Reproduce:

1. Download and import Test Pack.mcpack
2. Equip the first skin in the skin pack
3. Exit the classic skins menu

Observed Results:
The skin reverts to the previously equipped skin.

Expected Results:
The skin should remain equipped.

Video:
Minecraft 2021-09-28 18-42-19.mp4

Cause:
This is caused by the skin's localization name in skins.json consisting only of numbers. To workaround the issue, open skins.json in your skin pack, locate the affected skin(s), and add a letter to the localization name. This should allow you to equip the skin.