I have a 12004 which is a similar machine but higher up the chain.
You can't just pull out the dispenser drawer. It is designed to stay in, but you can get it out as follows:
Remove the top cover from the machine.
You will see several rubber hoses from the fill valves to the top of the dispenser. These hoses each connect to a plastic fitting in the top cover of the dispenser. The fittings are a bayonet type fitting into the top of the dispenser, to remove them you turn them a bit (quarter turn from memory??) and pull up and out. Once all of the fittings are removed from the dispenser, you can slide the drawer out.
Do you know what is wrong with the 10505?
I believe they had problems, they were not a great model. They were BOL over here at the time. Can't remember what the problems were, possibly motor/electronics?)
Good luck with it.