3498808 - DTP is failing with error: cannot insert NULL or update to NULL

DTP failed with the following error:

cannot insert NULL or update to NULL

Sometimes followed by:

SQL error with code '287'. See the following SQL message:
=> cannot insert NULL or update to NULL: TrexColumnUpdate failed on table 'db_schema:table_name'
=> with error: constraint NOT NULL violation;check StringColumn(): found NULL on pos XX;column 'XXX', 
=> table 'db_schema:table_name', rc=56
Exception CX_RSDHA_MSG logged
Exception CX_RSDHA_MSG logged
Roll back executed for data package 000001

• SAP BW/4HANA
• SAP NetWeaver

RSDHA014, RSDHA013, RSBK228, RSBK263 , KBA , BW4-DM-TRFN , SAP HANA execution in Transformation and DTP , BW4-DM-DTP , ABAP Orchestration of Data Transfer Process , Problem