See if the option to "Automatically open document styles" is selected in the Templates and Add-Ins dialog box. Clear the option and then redefine the style.

To open the dialog box: Click the Office button and then click Word Options. In the Add-Ins category, select "Templates" in the "Manage" drop down and click Go.

__________________
Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional