Crazy they would expect you to do a transition. I would not do a transition until after the balance has been paid and a hefty transition fee were paid. You should collect ASAP as they look to be on the verge of bankruptcy so collect what you can before other creditors swoop in.
Also, the fact that the software is not fully paid for perhaps means that you may have ownership rights - so the new team may not be entitled to touch or modify the code until the company pays for it. However, a lawyer is best suited to determining such details