Brother, DO NOT have the gear box opened!!!
under NO CIRCUMSTANCES, pay 50% if your car is under warranty.
I had an issue with the gears not shifting properly after heavy rains in Lahore last year and a dealership told me that the whole clutch set would have to be replaced and the gearbox will have to be opened. I knew better since my last chinese clutch plates on my Charade lasted for more than 150,000 Kms and was good to go when
I sold it.
As the weather became drier, the issue disappeared!!! Had I listened to the dealership, I would have spent thousands of rupees!!!
Later, the service manager at another dealership toild me that it must be moisture in the shifter cable... and that is my guess too. I am very soon going to remove the shifter cables and will lubricate those with either WD-40 or engine oil depending on what kind of cable it is.
Now this is another matter... there are cables with plastic interiors and ones with steel interiors (plastic on the outside).
Maybe all that needs to be done is to seal the cable ends properly. I do know that Liana's shifter cables come into contact with the gearbox linkages on top of the gearbox which is exposed to water when you have to wade through deep water (which needs to be done often in Lahore).