'Insert Slide Number' on template 'Master Slide' creates chaos when importing from 'My Templates'

As the title suggests ...

I built a template deck for a customer that incorporated the new Insert Slide Number functionality in the slide master. Now, whenever they pull a slide from My Templates, it creates an entirely new Slide Master in the project for each slide used. The end result of a 50 slide course was 51 slide masters, causing the program to lag or crash when Slide Masters is accessed.

Is this a known bug? Or does anyone have a suggestion as to why this may be happening other than the Insert Slide Number functionality? When I removed them from the master slides in the template file, this stopped happening.

Thanks,

Kevin