First of all, I hope you realize that using multiple Site Admin instances like this is just adding a ''burden'' to the server and too many QCP generation requests will at least slow down your entire ALM server activity.
It may have certainly caused the ''crash''.
During QCP creation, ALM uses the ''export'' folder as a scratch drive and writes temporary QCP files there as it creates them, then copies to your desired target location as it finishes.
If it ''crashes'' for some reason during this process, it will not have a chance to ''clean-up'' after itself, leaving the QCP files behind.
YES, you can and should delete all of these ''temp'' QCP files from this folder if you see any there.