How do I prevent PowerPoint from duplicating images when applying a template?

For years I've been puzzled about why my themes get "image buildup" (logos, pictures, sometimes text boxes). It gets quite annoying when I'm making a lot of changes to the themes and have to go in an update a set of presentations. That's when the buildup seems to occur.

I heavily use slide masters to provide consistency in my slides. When going through a heavy development cycle, I often will add new layouts to a theme but also edit existing layouts.

I suspect the duplicate objects occur when I attempt to apply the updated theme to an existing presentation. I haven't pin-pointed exactly when it occurs but I notice the problems after using the Design tab (apply to all slides or apply to matching slides or apply to selected slides.

I also create templates (POTX) files and set the latest template to my default theme (Design, right click on theme and set as default).

I don't believe images are duplicated when I create a new presentation from my template and copy the slides from the original deck and paste them into the new template-generated dec.

At my company, there are multiple people using the same theme and unless I've made a major update, we synch presentations periodically. We are all on Teams so I've added a folder with the latest themes in a central place. I want to create procedures to eliminate the image build up. Other than creating a new template and pasting slides into it, is there something else I can do to prevent images duplicating (sometimes 3 and 4 times)?https://answers.microsoft.com/en-us/msoffice/forum/all/new-theme-does-not-apply-correctly-in-powerpoint/4035d938-1a2f-4089-8f6b-a3a9f960f91b.This
I recently found this post from 2015 https://answers.microsoft.com/en-us/msoffice/forum/all/new-theme-does-not-apply-correctly-in-powerpoint/4035d938-1a2f-4089-8f6b-a3a9f960f91b.

He says "When you add an image / shape to a master or layout then under the hood in the XML PPT marks that shape as 'userDrawn= "1" '

In many circumstances when you apply a new template this is interpreted as "They drew it so they must want tokeepit!"  His hack is getting into the XML file and removing userDrawn=1 or setting it to 0.

Anybody else having these issues?