TD5 Series 2 Auto kickdown problem

Not sure if I'm posting correctly. Joined LZ about 10 mins ago.
The kickdown has started playing up in that when required the gear change doesn't seem to engage properly but rather 'jumps' between the two gears. Normal up gear changes seem to be OK. I recently asked my mechanic to clean the gearbox filter and check the oil level. He only managed to change 3 litres of the 9.5 litre gearbox capacity. Now when the engine is up to operating temp the kickdown seems to operate OK!

What should I do next?

Thanks and Merry Xmas.

kick down is operated by a solenoid controlled by ecu ,did it have this fault before oil change ?what was oil drained out like black or reddish brown?you should get 4-4.5 litres out and more if you let it stand ,did he refill it with engine running ,selector in neutral after cycling each selector position for a couple of seconds

The problem was worse before oil change.
Don't know about the oil - he didn't mention anything specific and I don't know what he did during change.
My additional problem is that I live in rural spain and the technicalities of this are too much for my Spanish!! Aaargh.
I can drive to an English mechanic (hour or so away) to go thru some more detail if I have to.

the oil has detergent qualities ,a box with very long oil change intervals can get sticky valves in valve block causing gear change issues fresh oil can help this or make a good box worse if the lacquer on valves was masking wear ,but oil must be refilled with engine running otherwise you wont get enough in ,incorrect oil level can cause issues too, if old oil was black box will need removing from vehicle and stripping as a clutch pack or 2 are burnt and box will only get worse till they or it are replaced

Eventually resolved the issue. Took it to LR dealer. Discovered that there was a problem with a tube to the Turbo. Hence insufficient power or kick down but sufficient not to show problem under easy driving !