@babarhyd - thanks a lot for valuable suggestions.
Last night, I visited Usman Autos (FB Area, behind Javed Nihari). This guy (Usman) is regarded as automatic transmission 'cheetah' by some other mechanics. I don't know him to be honest.
He checked my car and confirmed that its a gearbox issue. Additionally, he said that the foundation is not properly in place and jerking causes the foundation to hit body sometimes, causing a booming sound (has happened 2-3 times in last couple of weeks). Also, the accelerator pedal is a bit hard. He said it is quite likely that the old owner (or his mechanic) was aware of gearbox problem and tightened accelerator. With a free pedal, the problem would have manifested earlier. However he said that this could happen anytime, so I can't blame the seller for this (besides, there is no point doing this).
Usman said he would prefer to overhaul the CVT gearbox. He said he has done it many times and gives 6 months warranty for his work. Total cost (including gear oil Honda CVTF, 8 liters of that, costing 8K+ itself) is going to be 35K! This is huge, given that I've took the car ownership just a 3 weeks ago. But, anyways...
Usman said the gearbox replacement is an alternate option but there is no warranty/guarantee that the replacement would work flawlessly.
What to do now? Any suggestions?