Oracle:

Event reminders created on the server successfully synchronize to the device.  In the following situations, however, event reminders are not synchronized:

• Event reminders created on the device are not synchronized to the server.
• Changes made to event reminders on the device are not reflected on the server.
• Changes made to event reminders on the server are not reflected on the device.

These issues stem from a limitation of the Oracle software in regard to mobile data synchronization of event reminders, as noted by Oracle.   See "Alarm Behavior" in the following Oracle article for further information:

http://www.oracle.com/technology/products/cs/user_info/omobile_collaboration/html/mobile_data_sync.htm#generalconsiderations