Vostro 5402 Housing broken

Hi,

We've got four notebooks Vostro 5402 for our clients and ourselves. All of them had issues with housing or hinges - it looks that frame is coming off from the matrix, and everything is getting loose on the left side of the notebook (if all of them had the same issue, it can't be a coincidence). Dell responded, that engineers tested this model, and it's only users fault and it's not included in NBD warranty. Two of them broke after a year, next two after second year. Is it normal? This is first time when Dell declined our request, and it's the most problematic notebook we've bought in couple years. Even technical support knows about this problem, but can't do anything... Can we do anything about it?