@Micha Gerkema,Thanks for posting in Q&A.
From your description, I know that windows do not recognize the already existing user account on the device and continues to create a new profile on Intune managed device.
To clarify this issue, here are something you can check.
- Unenroll the device in Intune and left the device in Azure AD, then check whether it continues to create a new profile while Azure AD user's logon.
- Check if there exist the same issue on other Intune managed devices.
- Restart the device and check whether the issue will disappear.
Thanks for your kind understanding.
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