2000 S80 2.9

Over the last month I've had my cruise control just stop for no reason. Still indicates "Cruise" on the dash and most often can get it back on within a minute or so. May stay on again for hours or may kick back off within a few minutes.

Any ideas on what may be going on?

No codes/lights to indicate anything.

Car has < 80k miles with a xmodex throttle body I put on last fall. Only other mod is a K&N panel air filter.

 

I have a 2002 2.9 took it for a 5 hour trip last week. On the way down cruise control wouldn't work even after repeated tries. On the way back it worked fine. Don't know what’s up either.