Common Issues - Mustard2/MustardUI GitHub Wiki
Duplicating models not working correctly
Duplicating a model inside a scene will not create a new instance of the drivers necessary to correctly drive custom properties. In order to have another instance working as an independent model in MustardUI, do not duplicate an existing model in the scene, but Append a new one.
The add-on does not activate
Cloning the repository generates a .zip file with the wrong MustardUI folder name, as the name of the branch is appended. Either download the latest version or rename the folder inside the zip to simply MustardUI.