The visiting RE engineer had the entire rear suspension dismantlled, including the rear wheel, hub and the front sprocket. He found the wear pattern on both sprocs equal and hence they were put back as before. He then checked the spacer of the rear wheel and decided to change it, as also the spacer in the swing arm. Refiited everything back and I tested the bike till 130 KPH/81 MPH. It was stable, in fact I did try to weave it at those speed, but it did not oscillate.
Now for the tricky part (what the engineer did not know). The attending mechanic unknowingly added few shims on either sides of the rear shockers (upper bolts), cause he thought the gap was too big for the bolts to hold it tightly.
If you guys know, the Indian version comes with a seat pre installed which slots with the fastners where the rear suspension goes and its front is bolted the fram below the front seat. My two cents, the removal of the rear seat created a gap at the rear upper bolts which allowed the rear supension space to pull on either sides, creating the oscillation. I also saw the upper bushes of the shockers pulled sideways. Let me know if this theory holds any water.