If a component is installed within an assembly and this component is defective for whatever reason, it can happen that the checkout and checkin are grayed out/deactivated for the component in the Vault Addin. As a result, the above buttons are also grayed out/deactivated in the assembly. Instead, a checkin/checkout should be possible in the assembly + a note in the dialog that component X is not available or needs to be repaired.
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