Talked to tech support, it is a known issue, but requires under warranty replacement of device. We'll see how the replacement does over the next several weeks.
I went into a local corporate store today and had them connect me to their technical support. They eventually contacted HTC whose support/engineers had not seen the particular issue I had encountered. After some give and take, I got them to authorize a switch to an Incredible 2 (they originally tried to send me an incredible 1, which is EOL now, but balked at this suggestion). I guess the Incredible 2 is a reasonable approximation to the Trophy. As an alternative, the Trophy did have a $90 trade-in value toward a different phone with a special dispensation given to me for an early upgrade to get the 2-year price.
I really hate leaving Windows Phone as I think it has the best user interface and experience of any of the phones. Unfortunately, it's not much use if the hardware/software is unreliable.