Error when parsing process details or variables

Hi there,

I'm trying to get details about a typical error that I constantly seeing on a process. 

A little background: This process is suppose to read rows from the uploaded spreadsheet, based on row validation it has to complete two sets of DB updates. In current configuration these uploads are done when the valid rows are passed through a start process smart service. Since we have to update two different tables we have created a parallel flow after AND gate to complete the same. But the problem arises when one of the node completes and hits the end node and the other node waiting of the sub-process to complete. Please check the screenshot attached.

Consider to share the reason for this error and suggest the possible methods to avoid this.

Thanks,

Vishnu Devalla