I see unusual behaviour when opening tests via the JMeter GUI. I often run multiple instances of the GUI on the same machine when executing smoke screen tests after a fresh deployment of the application I am testing. If I open JMeter instances A and B and load tests A and B in that order. Then go to JMeter instance A and open the first entry from the Open Recent list. The first entry says 'Test A' but what appears in the GUI is actually Test B. Until now I didn't pay much attention to what appears in the left pane. Eager to find new defects in the application I test, I would just 'open recent' and then hit the start button. Because of this behaviour, unbeknownst to me I had the same test running in parallel in a few different JMeter instances and my test data exhausted a lot faster than I expected! :)
This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/4753