Translations once reviewed and saved in the TM are not detected as inconsistencies in other jobs (or split jobparts) while these are being reviewed at a later point in time.
So, when a reviewer comes across a segment that they once reviewed in another job, they have to remember whether that segment needed editing (as they are not warned of the inconsistency).
If they notice it, they can double-click the TM entry to replace the translation with their reviewed version - that is OK.
Available workaround (if any):
Jobs or split jobparts may be opened in a joined view to make benefit of repetition auto-propagation and the 'Inconsistent translations' QA check, but that is not always possible.
A highlighted warning/icon that appears in the Editors when the reviewer activates a segment that has the same source but a different translation in the TM. Ideally, the difference between the translations (active segment vs. TM entry) should also be shown.
Very often, a reviewer has to correct many jobs/jobparts in a project with different progress in the various workflow steps, so that using a joined view is impossible. Also, relying on the reviewers' memory is inefficient, especially if there is more than one of them working on the project.