To be honest, it can fall apart in the beginning, middle, or end.
Sometimes it doesn't matter how well the Realtor put s the Short Sale package together, seller's valid hardship, appraisal/BPO comes in at market value, etc.
You can be assigned a negotiator that is willing to work with you and then they are pulled off the file and you start all over with another negotiator. This can cause further delays and the foreclosure process does not stop.
We've gone through the whole process with "approvals" and at the last minute, the lender/investor throws another demand out. Some of which can be met, some can't.
You can start a Short Sale and it seems like it will go well. Other's start out "rocky" and continue throughout the whole process - you just stay on top of it through the end.
But again, there's no guarantee's that you'll get the home. If you're an all "cash" buyer, it may be best that you go for a "bank owned" or "standard" home so you can close quickly.