Confusing and inconsistent results are seen while testing a policy with similar file names in a given time frame.
It is best practice to upload your test file with a unique name including a date timestamp. Example, [dd/mm/yy].test1.420PM.txt, [dd/mm/yy].test2.422PM.txt.
While events are usually FI/FO (First In \First Out) there is no guarantee that it will always be the case.
A unique file name helps Support and the Customer track events from end to end.