The latest bedrock beta build introduced capes in the custom skin editor;
However, in the process, it broke all capes present in the Minecon 2016 skin pack;
When attempting to set a skin with one of those capes from the skin pack, the cape in the preview and in-game is not visible at all.
Steps to reproduce bug:
Launch Minecraft Bedrock v1.14.0.3 Beta on a Windows 10 machine;
Open the skin editor on the bottom right;
Create or modify an existent skin in the skin selection menu;
In the skin pack menu of the skin editor, choose one of the Minecon 2016 skin pack's skin. Ensure that the skin is supposed to have a cape attached to it;
Notice the issue in both the preview and in-game.
Confirmed by Community Consensus. Another report (MCPE-53933) has uploaded images that show the capes are missing in previews for both the Minecon 2016 Skin Pack and for the Founder's Cape on the Capes tab in the Profile. This is a recent change, because the capes are visible and work fine in 1.13.0.