Why is my ISO's sha1 file deleted every few days?

Every few days I deploy my in place upgrade fixlet and for some reason, it fails. Then I check the server and see that the file is missing so of course it fails.

I’m not sure why it happens. Can someone explain what I’m missing?

Its possible that your server/relay cache size is set too low and the ISO is being purged to make room for something else. By default the cache limit is pretty small. You can increase it by using the “BES Relay / BES Server Setting: Download Cache Size” task in the BES Support site.