Australia was talking about walking awa6 from the deal over 2 years ago - the nuclear sub part of the AUKUS treaty negotiated over the last year or so is a consequence of Australian dissatisfaction, not a cause of it.
Reference break clauses and penalties, these were also discussed and identified - a price Australia is obviously willing to pay to wash their hands of it.
https://www.abc.net.au/news/2019-05-...sinks/11112952