K
No.
It still comes back to a question of responsibility and 'the contract' (whether written or implicit) between you and your customer.
It still comes back to a question of responsibility and 'the contract' (whether written or implicit) between you and your customer.
You used the term 'subcontract', which leads me to think that the distribution forms part of your system, but is a service that you choose to outsource to a third party. (It would help if you provided rather more information than you have BTW, because we're having to guess at what you mean).
In that case, treat the 3rd party as a supplier which they are, and just ensure you meet the requirements of the Purchasing clause. Their system is their responsibility - yours is yours. But you do have a responsibility to take care in selecting suppliers and to monitor how they perform. (And naturally, do something about it if performance isn't acceptable.)