Nanny for your supplier?

The worst situation you as a project manager can end up in is the where you have to help your supplier to deliver that which this particular supplier was originally carefully selected to be best at. Now it turns out, unfortunately, that the supplier  nevertheless not really has the capability, but since you did have large fingerprints on the choice and the decision of the supplier, you can not quite tell you free of guilt, and you feel therefore pressured to help the supplier. Once you've done this a few times, you are so entangled in the case that you can not stop. Either the supplier succeed and therefore you or you will go down together!
What went wrong? Yes, it was either in the selection or in your handling of the first signs of a lack of ability to deliver.
In the selection process could be: 1) No supplier met the requirements you had set. Instead of realizing that you and your client / boss / management may reduce the requirements, you get it legalized taking the best of them instead - and then you're already into it!
2) You thought that it is the supplier's own problem if they claim they could provide and then can not do it! But the reality is, because your client / boss / management can not wait for the supplier to get a grip on things, or you find another - "there are millions at stake ..." echoes in your ears when you try to fall asleep. It ends again to be your problem.
At the first sign it could be: You failed to use the contract to what is actually being written for
You showed confidence rather than seek certainty
You showed understanding in the hope that they probably would quickly solve the problems

So you have been warned! It is not about being tough on suppliers. No, it is about certainty!