We have been unable to reproduce this error during our testing. Can you provide a repro project to help us investigate further? Please PM me the link.
Hey medabit, having the same problem as most everyone else with Updating.
The Migration guide here: https://library.vuforia.com/articles/Solution/How-To-Migrate-a-Unity-Project.html#migrating-6-2 says to Download the "ConfigurationUpgrade.cs", but there is no Download link in the guide:
Download the upgrade script ConfigurationUpgrade.cs and add it to any Assets/Editor folder.
It just contains a link to the page with the Script that can be Copy/Pasted into a Unity Script afterwards: https://library.vuforia.com/articles/Solution/Unity-Configuration-Upgrade-Script-for-Vuforia-6-2-plus
As other people have said in another topic: https://developer.vuforia.com/forum/unity/migrate-v505-v62 regarding this, immediately after Copy/Pasting it from that page as Assets/Editor/ConfigurationUpgrade.cs one gets these Errors in Unity:
Assets/Editor/ConfigurationUpgrade.cs(74,25): error CS1525: Unexpected symbol `bs'
Assets/Editor/ConfigurationUpgrade.cs(352,33): error CS1525: Unexpected symbol `1'
This can be fixed by adding a "?" to lines 74 and 352 so they look like this:
var name = idx < 0 ? bs.path : bs.path.Substring(idx+1);
WriteProperty(property, value ? 1 : 0);
So far so good, but afterwards one gets the Error:
Assets/Editor/ConfigurationUpgrade.cs(327,60): error CS1061: Type `UnityEditor.SerializedProperty' does not contain a definition for `GetArrayItems' and no extension method `GetArrayItems' of type `UnityEditor.SerializedProperty' could be found. Are you missing an assembly reference?
Could it be that you worked on the Script on your side and haven't offered as a download or updated the Live version on that page and that's where the problems stem from?