Have you gone into test mode for the T-Rex to see if you can make him turn there? When you say intermittent, do you mean that some days/games he will turn back and forth normally. Or that when he does turn he will do so in a kind of start and stop fashion?

If it is the start and stop one, then it sounds to me like there is no connection issue. Sporadic movement is the normal symptom of a bad gearbox. Google the T-rex motors and you will get plenty of information on how many problems there are with them. Essentially your gears are likely shot. Most people with this problem just turn of the left right movement because as long as the T-rex eats the ball, they are happy. The motor can be pricey.

If you do replace the motor, make sure you update your roms, as the newer code puts less wear on the gears.

Nope. It is uses rapid pulses to the motor instead of full power on and off. It is supposed to cause less wear on the gears.

Lots of topics on it out there.