Error message when changing bank data in ESS

Whenever a user tries to enter a new bank detail in ESS on portal, i.e. Personal Information > Bank Information > New bank, the system returns the following error message:

"Type conversion error, field BEGDA, complex type class com.sap.xss.hr.per.gb.bank.model.Hcmt_Bsp_Pa_Gb_R0009"

Is this a known error in ESS? can you please point me in the right direction for solving this problem?

Many thanks

John