Hi Pieter,
Thank you for posting your question on Microsoft Office Community.
Before we proceed, I need more information to help you better.
- Is the issue specific a particular file?
- Is all the Office updates are installed in your computer?
If the updates are not installed, you may install the updates and check if it helps.
Please follow the below steps to install the updates.
- Click on File on the ribbon PowerPoint 2016.
- Go to Account in the File Settings.
- Click on Update Options and click on Update now.
- Wait till the time updates are installed, verify the result.
Please get back to us with necessary information, we’ll be glad to assist you further.
Thank you.