2001 E39 525 touring kickdown problem

[Lornamac]

Wondering if any of you kind people can shed light on my problem. The automatic gearbox works like a dream except when I use the kickdown. It kicks down fine but the problem comes thereafter when it should be changing up again. It just revs and stutters until I lift my foot from the throttle a little, then it will change up, but some momentum is lost. Any ideas? Only done around 48k miles.