The automation engine is automatically generating an extremely high number of system forced memory traces.
When the error occurs, the following messages can be found in the WP log files:
U00011801 Error in server routine 'UCDS_R  ', server: 'UC4#WP004' AE-System: 'UC4'.
U00003422 WARNING: Cannot load conversation memory '042f2651' for server routine 'UCDS_R'.
U00015006 System forced memory trace dump

When using nested workflows, a child workflow tries to update an inherited variable with a new value. 
In the nested foreach workflow, the Publish Value is originally saved (only possible when using the JavaUI) in lower case letters. 
In the AWI the Publish Value is always shown in upper case letters.

Screenshot from the Java UI:

<Please see attached file for image>

Screenshot from the AWI:

<Please see attached file for image>

So, for the same RunID you have two values of the variable &item#, one in upper case letters and one in lower case letters, which leads to a unique constraint violation.
 

Oracle Database

A correction was made to handle case sensitive Publish Values.

The correction for this issue is available on the following versions:

• Automation Engine 12.0.6 
• Automation Engine 12.1.3 
• Automation Engine 12.2.0

Please install one of the above listed versions or a higher version to resolve this issue.