First series Ford Fiestas experience issues with injection pump pulleys, which work loose and generate vibrations in the belt. A consequence is ‘jumped teeth’.
On a general note, the OE timing belts in the Synchronous Belt Drive System (SBDS) have a ‘dimple’, but Gates points out that its OE quality replacement belts and aftermarket replacements in general do not. There is no cause for concern.
Excessive noise inside the SBDS has been attributed, on some models at least, to rust. A careful inspection is recommended.