1989 LeSabre cruise control problems 3800 V6 AUTO OD TRANS

Cruise will work but seems to forget what it is doing and looses speed. When it does this it will not respond to any input such as hitting resume to speed up. If you hit the gas pedal it will remind it what it is doing and may accelerate back to set speed sometimes not. If you accelerate back to set speed with gas pedal some times will hold speed sometimes not. Any time when it is set and you hit brake and stop or slow down then resume will take it back to set speed until it forgets again.  When set and working will respond to input from control switch like accelerate or decelerate. ANY HELP WOULD BE GREATLY APPERCIATED THANK YOU