Disco II gearbox noise

[db1047]

My Discovery II TD5 automatic, 2002 model leaked transmission fluid yesterday while I was driving. The feedpipe came loose and the car lost all its transmission fluid. Most of it drained out only after I stopped. We took it in to the LR workshop and they just had to tighten the feedpipe nut and refill the transmission fluid. When I got my Discovery back from them the first thing I saw was that the "Manual" and "Sport" mode lights were flashing on and off. After switching the ignition off and on again the problem went away. The second thing I noticed was that the gearbox made this clug sound when engaging the reverse gear. The guys at my LR workshop say all the Discoveries makes this noise. I'm sure mine never made this noise before the leak.

If someone could please help, what is causing this noise?

Thanks