The XPS is a known - nonworking ESC with Spektrum. There are lots of posts on this on one18th.com. The XPS is looking for a signal within 2 secs and doesnt get it from the Spektrum during that time.

However, If you are willing to simply reset your XPS everytime you run by holding down the set button (with the Spektrum already turned on) while you power up the ESC it WILL work. It is not a big a pain as it would seem after a while. I even have a small hole drilled in my body so I can do it with the body on.

If you go through the setup and you get reverse and only want brakes with no reverse. Just turn off the XPS and reset it again.

Once you get the XPS reset - you can then set up full throttle, neutral, brake, etc...

This is the only fix - unless you change the ESC out (or use the stock radio - which I refuse to do).