CRM BT Extension Issue: Custom Handler Classes

Hello CRM gurus,

I'm working on a project to extend CRM object Business Transaction with new nodes and encountered an issue.

I configured the new nodes and new relations, developed my own custom handler classes inheriting CL_CRM_RUNTIME_BTIL and redefined methods READ_ATTRIBUTES and MAINTAIN_ATTRIBUTES. I also used CRMV_EVENT to register call-back function modules which were invoked by function module CRM_EVENT_PUBLISH_OW from my customer handler. When I conducted testing in transaction GENIL_BOL_BROWSER, it worked fine to insert a new entry, the Z*_RUN_BTIL-MAINTAIN_ATTRIBUTE method was called and I can see my Z* tables did get updated. However, Z*_RUN_BTIL-READ_ATTRIBUTE was never invoked. Every time I inserted an entry, I can no longer see its existence in GENIL_BOL_BROWSER and have to check it in SE16. It puzzled me a bit as both methods MAINTAIN_ATTRIBUTE and READ_ATTRIBUTE are in the same customer handler Z*_RUN_BTIL. What could be the reason? Would you please shed some light if you have a clue? Many thanks.