Freezing(crashing?) sure sounds like a software problem and obviously
buttons should not get stuck under the face plate so that would be a
quality or design problem. Have you brought these problems to TI's
attention? If so, what response have you recieved? Have they offered
to replace the handheld units that have button problems? And have
they indicated that they will investigate and attempt to fix the
freezing problem in a timely manner? Since the npsire series of
products is rather new in terms of volume production and debugging, I
would expect TI to jump on this situation and give you some immediate
relief with replacement units for the sticking button problem and
commit to a date when they would get back to you with the results of
an investigation into the freezing problem. Don't give up on these
issues. Your school has spent a significant amount of money on TI
products and deserves products that work properly and I am sure that
other teachers will want to know what sort of support and resolution
you recieve on these issues. Please keep us informed.