Hi @Rasmus Lundgren
Could you please tell us where is the template stored, such as on a shared network location, on a SharePoint organization assets library?
Do you mean this issue occur with all users?
Please check following threads:
Understanding the behavior of "Use Destination Theme"
PowerPoint - Use Destination Theme does not work when copying a pasted content
Try to create the new template from your old template, taking care with legacy layouts not to delete any slide layouts, change any layout names, or delete or add any placeholders.If the charts can be obtained from Excel workbook, I suggest you import an Excel chart, check wether this issue persist.
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