Certain types of adjustments (eg enterprise fees) cannot really be changed arbitrarily; when the order is saved and "recalculated" the values will be reset. The adjustments are still shown in the main order edit tab, but are not editable in the adjustments tab.
We have a PR already that removes the UI for this when the order is
canceled. Implementing it on controller-side makes sure that it doesn't
happen accidentally if the user has multiple tabs open.