There is something very wrong with this. Someone, somewhere has failed to deal with all aspects of the supposed 'clean break' that was agreed. 

If you agree one party to proceedings will stay in the house until it is sold there is usually a good dose of trust and compromise on both sides. The person leaving the family home trusts that the remaining party won't scupper the sale, and the person staying will have to compromise and pay more bills while they are there. 

Having said that, it doesn't matter if they are millionaires or on a limited budget, their lawyers should have thought about the interim arrangements and should not have left them vulnerable to further proceedings and costs.