Problem

Saeco SG200 and similar vending machines has a nasty bug - if customer made selection, and start credit card transaction, the whole vending machines will go into a limbo mode.

Story

Saeco SG200 is a nice standalone coffee machine. The coffee from this machine may taste ok, but besides maintenance, this vending machine allows customers to make selection first, and tap credit card.

In MDB, this selection first, start payment later should be implemented as AlwaysIdle feature. However, Saeco engineers decided to cache the customer selection and postpone that after BeginSession instruction.

As Murphy’s Law described,

Anything that can possibly go wrong, does.

They screwed it up. If customer make selection first and then tap a credit card, these machines will immediately issue a VendFailure as response to VendApproval, and put itself in limbo mode. SG200 will immediately do a full power cycle by itself, while other poor vending machines will stay in limbo mode until someone manually unplug the power cord.

In limbo mode, these machines will not take any coins/notes or credit card. Nothing will dispense. Make sure you monitor this behaviour if you have one of these Saeco machines.

Solution

Contact your technician. Upgrade firmware might work. Unfortunately we don’t know.