Signature

If you went to Red Lobster and they were out of lobster you probably wouldn't go back.

If you went to Starbucks and they were out of coffee you would never trust them again.

If you went to Buffalo Wild Wings and they didn't have wings you would take your business else where.

These are what we call signature items. Its what these brands are known for.
711 is known for their slurpee. Not their gas, service or coffee.

Why then is the machine broken 60% of the time?

Shouldn't you put every effort towards making your signature item as perfect and flawless as possible?

When will customers finally give up and stop going?