There are significant differences between the tail lights of a 1985 and older 240 and a 1986+ sedan. Since you mention having a 3rd brake light, you must have a 1986+ model.

Thing to check: (1) find out if your tail light units are right for the car. Do this by looking at the date stamp on any red or yellow tail light lens. The number in the center circle should be either the year of your car or one year earlier. If it is older, someone replaced the unit with a wrong one.

(2) The 1986+ unit has a circuit board with a number beginning with 6, not 3.
The "3" board will mess up a 1986+ operation.

(3) Check the color of the bulb holders in the lower outer lights. Black on the left and white on the right.

Failure of any of these can help explain your situation. Post back with what you find.

Good Luck,

Bob

:>)