A family of Microsoft word processing software products for creating web, email, and print documents.
It's possible that the documents are being opened on a computer where the user has the option set for "Automatically update document styles" which is causing the styles that you have defined with the corresponding style from the user's Normal.dotm template.
You can easily re-instate the numbering by clicking on the Document Template button in the Templates section of the Developer tab of the ribbon and then select your Lease template.dotx as the template to be attached and temporarily check the box for "Automatically update document styles" You should not however leave that box checked.