I think the first weak move in this game was starting a 1-1 ladder chase (moves 10-13) without a downstream peg.
For example, |10.k11 is one of many possible downstream pegs here, and it has the added benefit of weakening the h10-o14 connection. Then, let's say White responds with 11.t10, because White has his back against the wall at this point, but now the ladder chase works - 12.n1713.m1614.m1515.l1416.l13. However, White's defensive t10 peg was also a downstream peg! Unfortunately for White, it's probably too weak across the top: 17.r1818.s6. So, that's just feeling out the strength of the move, and it seems strong. There are too many possibilities that early on in the game to predict how White would actually respond.
First, look at
26.l6
so, now I see it again :(
For example, |10.k11 is one of many possible downstream pegs here, and it has the added benefit of weakening the h10-o14 connection. Then, let's say White responds with 11.t10, because White has his back against the wall at this point, but now the ladder chase works - 12.n17 13.m16 14.m15 15.l14 16.l13. However, White's defensive t10 peg was also a downstream peg! Unfortunately for White, it's probably too weak across the top: 17.r18 18.s6. So, that's just feeling out the strength of the move, and it seems strong. There are too many possibilities that early on in the game to predict how White would actually respond.