Yes the problem is in the stock tyres . I have faced same problem while trying to climb an incline from my driving side with 7 people on board while going towards pc bhurban. The tyres were slipping and had to back up and race up again. But next time I took the wide turn as all the other cars were doing and then no problem. but general tyres have poor grip , and i have come to know about it just 2 months back..
by the way brv has got good power as my manual gearing is short . goes to 100 km in less than 11 seconds.
Unfortunately i cannot now change my tires as they have been run for 1000 km and i would get too low price for them, so i have decided to run them till their natural life