Bad batch of Vostro 15 3510s (hinge issue) and an account manager who now ignores me

Has anybody else experienced an issue with Dell Vostro 15 3510 devices where the hinge is too stiff that it rips aware the casing from around the screen?

We purchased 50 of these for one of our clients, and 21 of these have now broken with the exact same issue. This has been happening over the last year, and I have had a case open with our Dell Account manager for this entire time who has not been able to help at all (keeps telling me to just call the standard customer support number despite this clearly being an issue with the model or batch), and has now just been ignoring all communication for the last 1 month!

I have no idea where to turn to now, as our account manager's own manager is also ignoring all emails from me, and I have a very angry customer who has bought 50 laptops but now has staff who do not have a machine to work from.

The customer wants a refund or all 50 replaced with upgraded models with compensation for lost time. 

Is anyone aware of a complaints or escalated support team?

Thanks,