Question the Implementation

Environment:
Application: Windows application
Operating System: Windows Vista

Requirement:
Whenever Agent hits Button (say Close Call) ,the application should close the session and the same time it should generate an XML should store in a table.

Implementation: Whenever Agent hits the button instead of directly storing into data base application temporarily stores in local machine and then stores into the data base. Once application stores the XML in the data base application will delete the temporary file.

Repro Steps:
1.Launch the application.
2.Do some operations in the application.
3.Click on Button.(Close Call)

Actual Result:
Application crashes.

It happened only in UAT environment in all the machines and Testing environment it never happened. After UAT people reporting the bug ,we tried but could not repro it. After going through the log file we came to know that application is crashing while writing the data into temp file ,meaning application unable to append the data to the existing tem file because of some corruption and then it crashes. Then the implementation has been changed to like this
whenever agent hits the button ,before writing into temp files application deletes the old file and creates new temp file.

Finally ,what I would like to Conway is as a tester it's not enough to cross check the functionality with respect to document we also need to check (if possible test )how the functionality is being implemented.