Error message when data sources have duplicate column names

Hi,

Since this Monday, I've come across an issue with ALL customer life cycle campaigns.

For these campaigns, I declare the CUSTOMER_ID_ from my CONTACTS_LIST in data sources and then declare the supplemental table with CUSTOMER_ID_ from this table as the lookup key.

Since Monday the following error comes up:

The column CUSTOMERID exists in multiple data sources. Columns with the same name can cause issues with personalisation and using aliases will not prevent this problem. Please rename the duplicate columns.

When I rename the column CUSTOMER_ID_ in my supplemental table, I get a different error saying that my extraction key doesn't fully match the CONTACTS_LIST (as the extraction key for my supplemental table is also CUSTOMER_ID_).