Two problems related to door latch have been reported for the 1998 Mazda Protege. The most recently reported issues are listed below.
Coverings on driver and passenger side key locks that prevent moisture from entering the lock were made from plastic. This plastic becomes brittle after several years of exposure and use and can break. When the part breaks, pieces from the broken cover can easily be lodged in the lock rendering the lock unusable (as happened to me).
Driver and passenger side plastic door lock covers broke, consumer had them replaced with metal ones to prevent future breakage. Nlm.