1.4 automatic: kickdown not returning
 

I have year 2000 Saxo 1.4i with 3-speed automatic gearbox, 120 000 kms. Pushing the gas pedal down changes nicely from 3rd to 2nd gear for better acceleration, but lifting the pedal does not always change back to 3rd. Pulling the gear lever manually to 2nd and back to 3rd makes the gearbox change to 3rd.
Apart from this issue, the gearbox works fine. Gearbox oil has been changed a couple of times in last few years. It may not have been changed in the first 15 years though.
Is this a common problem? Any idea how easy or difficult to repair?

Does it stay stuck on 2nd forever after a kickdown event? Or does it eventually go back to 3rd. It might just be lazy due to age related wear.

It seems to stay stuck on the lower gear "forever".

But it normally goes into 3rd when you are driving, it only gets stuck when you kick down?

Could be an electrical fault or maybe there is dirt in its valve body.

It will be hard to diagnose without either ignoring it or getting it stripped down and cleaned/rebuilt.

Yes, it goes fine into 3rd when accelerating normally, that is, without kickdown.

The issue can indeed be an electrical fault, maybe a bad connection in some cable connector. Any idea where the kickdown on and off signals go from pedal to gearbox?

I'm not sure, it might be a vacuum hose to a sensor on the gearbox ECU. I'm not too familiar with the auto boxes in these cars, they're relatively rare.