What is the ruling on requesting a new machine for free from the company without knowing the reason for the old machine's malfunction, and is it obligatory to buy another machine given the possibility of my having caused its malfunction?

Since the company agreed to send a new machine after you mentioned transporting the machine by car, there is no harm in requesting them to send it, based on their agreement, regardless of the true cause of the malfunction. This is due to the generality of the Prophet's (peace be upon him) saying: "Indeed, the wealth of a person is not lawful except with his willing consent."