The incentives here are all aligned against quick repair: Taylor makes more money when machines are broken. McDonald’s corporate has a lucrative service contract with Taylor. As a result, poor franchisees, who have no choice about what equipment to buy or how to service it, are forced to deal with broken machines and annoyed customers.
Surely, franchisees and potential franchisees talk to each other, and if any appreciable amount of money was going out the door to fix the ice cream machine repeatedly, it would be a known cost of doing business.
If the full extent of the repairs necessitated by the behavior were clear, obvious, and known ahead of time, then yeah, this would strictly be worse. But a slightly lower, but secret, fee might be preferable to a higher but obvious fee.
That's just me speculating though. Could also just be incompetence or maliciousness, or maybe just once upon a time a particular person in McDonalds corporate took a bribe to make it happen. Who knows.