When I've had problems like this with templates it has been because of the interplay of my hard drive and the Microsoft cloud's OneDrive automatic backup. Essentially your templates might be synchronised in two locations and Word could be finding it hard to have exclusive access to the template because of this.

It is worth exploring your folder settings to work out what folders are automatically backing up on OneDrive and stop that from happening with your templates to see if that allows your templates to work more like the good old days.

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Andrew Lockton
Chrysalis Design, Melbourne Australia