it may be situational. There are some long sloping hills between Boston and Hartford CT on I-84. If, I'm in cruise control I can feel the car braking then, accelerating then braking, the "speed" sensor jumps back and forth. I usually flip it off here.
I've got a '97 OBW as well, in the same area, this car drops into a real low gear (yeah, both automatics), and almost red lines trying to get back to speed quickly.
My previous car as a 5 pd and, anything lower than 5'th and relatively level road would cause cruise to disengage.