To resurrect this topic in case anyone else searches for this problem....
I have just bought the Altair 60mm finderscope and have found exactly the same focus problem that the OP had.
I have been advised by the shop that Altair have advised that the focus allows +/- 5 dioptres which should suit most users.
I assume that the inference here is that it's my eyes that are 'at fault' not the scope.
I have no issues with any other optical equipment that I own.
So I assume that if anyone else has this issue, it is inherent in the design of the eyepiece.
Oh and hello everyone! I'm new here, based in South Lakes Cumbria UK