MGF 2000 Steptronic trouble

My MGF 2000 MKII Steptronic auto trans is not operating as I think it should.

To explain! Under light accelerator pressure the trans operates well until you accelerate hard or when you come to an incline requiring more accelerator pressure, then I get hunting and vibration from the transmission, It seams as though it is searching for a new lower gear and can't make its mind up or the kick down system is not working.

If I back off the accelerator the vibration stops.

When this happens I have to resort to driving it in sports mode, but still under severe conditions the symptoms return, but not as noticeable.

Has anyone had this problem and can advise a solution.

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