There seems to be a problem with the T-Mobile HTC Sensation 4G, and it's the same problem that Apple iPhone 4 once had...what some may call the death grip problem. The T-Mobile HTC Sensation 4G has recently experienced cellular signal problems once a person picks up the handset and places it in their hands. Not only does it lose its cellular signal, but it also affects the Wi-Fi and Bluetooth connectivity.
What is causing this problem? Nordic Hardware believes that it is the back cover. The back cover is metal, but the cover also has plastic places that represets the antennae part of the device. When you place the HTC Sensation 4G into your hands and it covers the plastic parts, this is when connectivity to Bluetooth, Wi-Fi and cellular signal is lost.
Placing a protective cover or case over the phone will do no good due to the fact that the case will only block the antennae part of the phone. HTC is aware of this problem and will be taking steps into fixing it.