aesalon: No the solution was correct. (a bad ko for white is best that black can get)
The problem with F18 is that white can A16 and now it's a direct ko.[current position] + A16
aesalon: You have the wrong refutation for A18A19E19D19F18 since there would be life after squeezing. The correct refutation is A16 and it is a direct ko.
posetcay: It is possible to live without ko, fixed the solution.
Ok that is a nice refutation, it seems that I misunderstood your initial comment, updated the solution tree.