I'm getting this error from the nine verb package:
You are trying to replace or create a Prefab from the instance 'AdditionalScripts' that references a missing script. This is not allowed.
Please change the script or remove it from the GameObject.
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)
It also seems to be missing HighlightDefaultIcon and ItemStelLabel:
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Comments
The package no longer makes use of those scripts - they have been merged into the ScummInterface class.
Missing MonoScript components can be removed, though they should not be present on the latest version of the package.