D1 Transmission - Slow/now downshift

OK, a typo. That was supposed to be "...slow/no...". Sorry.

Recently the transmission on my '97 D1 began exhibiting a downshift problem.

When slowing to a stop it only shifts to 3rd. It will shift to 2nd or 1st if the selector is moved.

I am not an automatic expert but am wondering where I can find some diagnostic info for this transmission (4HP24, right?) as implemented in Land Rovers.
 
So the fluid was very high. Nearly 1.5 liters. The dipstick then showed the correct level at cold idle.

Two or three laps around the block and the gearbox returned to its former normal behavior.

Lesson Learned: Don't assume the fluid level is correct regardless of who did the service.

Sorry to waste anyone's time.