StephaneLamy:
It seems the false "correct sequence" pointed out by tatesin is still there in the tree?

Tatesin:
Hi! The problem gives as a correct solution the following: Q1-Q2-S2-R2-S3-etc. If you answer S3 instead of R2 and then continue R2-Q3, I am pretty sure it doesn't work? I think you have to play S2 as first move.