I have been approached on several occasions where a 3rd party has created something for a company and it just doesn’t work. It usually goes along the lines of the company asking "Could you spend a few days fixing it?". More often than not, it’s something only a rewrite will fix
I have also been approached on more than one occasion by offshore companies (I don’t mean to imply all offshore companies are like this) where they have won a job on the strength of claims on their web site but they lied and didn’t have the capability to do the work. Finally, I have seen several occasions where mobile software has had to be rewritten to make it scalable or more flexible.
All these scenarios can end up being costly, take extra time and jeopardise your project. Use people who have done this kind of work before. Look at their case studies. Get references. Get referrals from other companies who have had similar work done.
All this seems obvious. So why does it come up so often?