[lmm]

> Well, as far as I understood, Scrum's fundamental principle dictates that the team delivers working software at the end of every Sprint.

Working software yes. If you break the build the minute before the end of Sprint then yeah you better fix it. Sensible teams resolve this by not committing at the last minute, and by having the Sprint end at, say, midday Thursday, not 9AM on Monday.

> if the team fails to judge correctly, it has to do what needs to be done to fulfil its promises.

Nope. There are no promises, no "clear obligation". Half the point of the daily standups is that if a feature is not going to be deliverable in its original form within the sprint, you catch this early, and then you talk about it, you have contact with the product owner, and you decide something sensible.