Unable to edit communication data coming from ECC

Hi,

we replicated customers from ECC to CRM as part of the legacy data migration. In the following CRM is the leading system for the customer maintenance. The problem we have is that the communication data that came from ECC cannot be edited and changed in CRM. The data simply gets wiped out when I hit enter or the save button. So this means that I cannot e.g. correct a phone number in CRM.

If I maintain the data in CRM initially, I can also change it afterwards.

The following fields are affected:

Phone/Extension

Mobile

Fax/Extension

E-Mail

Website

Any ideas why this happens?

Thanks

Nicole Lange