Well Verizon is sending me a third Vortex as the first two had the same problem.
During a call about half the time it won't allow me to hang up. I hit the icon and it changes appearance as though it accepted the command, but it doesn't hang up the call. I have to power the phone down to end the call. It seems to happen most often during voice-mail retrieval, but also during normal incoming or outgoing phone calls. . . I can find no pattern. It will also not allow me to enter passwords and such when I try to log into my bank, or other accounts over the phone. Once again it looks, and even sounds like it accepts the command, but nothing registers from the other end.
I have wiped (factory reset) each of the first two phones completely and didn't install any other apps, and left it completely native, and it still has the same issue.
I sure hope the third phone they're sending me is the charm.