TA1600 Locking up

Anyone else experiencing issues with the TA1600 where it randomly locks up and has to be rebooted?  We have three of these units installed at a nursing home and are experiencing this issue.  We opened a ticket with support but they are no longer responding to our inquiries or phone calls.  They should be held liable if a customer needs to dial 911 and can't do so because the ATA is locked up.  Pretty sad that they won't provide support for their product.