This is what I found about Sobers.
1. Sobers visited New Zealand as a teenager in 1955-56 when he was far from the finished product. Was just seen as a promising upcoming batsman. He scored 81 from 5 innings. 2 of them were run outs by the way
Bear in mind that he did not bat well against anyone in this period, not just NZ.
2. He did not visit there again for a freaking 13 years. Fast forward 1968-69, he had a great tour of Australia. Averaged closed to 50 with bat and bowled more than 200 overs. Despite this tiring schedule, he decided to play in NZ and the result is there for every one to see. 70 runs in 5 innings.
Based on this evidence of 5 innings when he was a teenager and 5 innings at the end of a tiring trip, is there a way to say Sobers had a weakness against NZ ?