This Error:
The server did not receive a response from an upstream server. Request tracking id '08585831622344535876327437513CU09'.

The child flow in question parses a number or parameters and writes lines to excel based on inputs. Several 'forks' in the flow terminate with 'success' by design:

...but in these situations the parent re-engages the child flow multiple times (as above, '4 retries occurred') and the excel ends up with correct entries but multiple lines of the same.
Can the issue be with the response call? Or is this behaviour a bug?
Any help certainly appreciated!