In Scrum, the team has the power to bring a sprint to a premature end if it becomes clear that the Sprint Goal cannot be achieved (or if it becomes irrelevant).  How can a SAFe team do the same thing?

Although I have actually done this once, what we did was really made up on the spot, so I'm looking for some tried-and-tested suggestions.  Also, we were in the fortunate position of having no dependencies to/from other teams in the Release Train, so after cancelling the sprint and holding a brief retrospective, we were able to re-plan the remainder of our PI without having to involve other teams.  But I would like recommendations for what to do when the situation isn't quite so simple.

Due to the Release Train synchronised cadence, we ended having to plan a half-length sprint so that our end date aligned with the other teams.  Is that the Right Thing to do?  And do we need to perform an Iteration Review for the aborted sprint?

**As a Scrum Master, what do I need to know, to guide my time through this potentially stressful time?**

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N.B. this question is not the same as [What is the framework "escape hatch" for a SAFe ART that is running down the wrong track?](/q/23448/35563), as that is about the entire ART discovering it can't meet its PI Objectives, whereas here I'm talking about a single team and a single iteration (though we obviously expect a knock-on effect on the subsequent iterations).