How to debug error code HTTP 500 -2130575336

Question

Dear Sirs,

 

I've got the error listed above in a Sharepoint 2013 workflow.

 

Although the text  is quite clear

 

 

 

I am not able to understand which column generated that warning message.

 

Could you kindly suggest a method to find where the error arises?

 

Many thanks for your help.