I just looked again at my TS55 and found the metal tap you referenced.
On my saw, the tab is not jammed into the plastic. Its function is to prevent the saw from being plunged unless the trigger is pulled. When the trigger is pulled, the metal tab retracts and allows the saw to be plunged. If the metal tab is jammed into the plastic, my guess is that it cannot retract and the saw cannot be plunged.
I'm a user and not a trained Festool mechanic, but the function looks simple.