@Marc Henika, Thanks for posting in Q&A.
For the setting "Automatic app updates", when choose yes, Intune detects the VPP app updates inside the app store and automatically pushes them to the device when the device checks in. For apps deployed with Available install intent, the automatic update generates a status message for the IT admin informing that a new version of the app is available. This status message is viewable by selecting the app, selecting Device Install Status, and checking the Status Details. Here is a link with more details:
When it is turned off for VPP, I think you need to delete the old app and add the new app again to deploy the updated one.
Hope it can help.
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