No doubt, it is a Poser 2012 bug:

From your exported 2012 piano

line 18380
vn -1.00014 0.0117139 0
vn 0.999748 0.00409131 0
vn 0 0 0 vn 1.00024 9.31469e-005 0
vn -0.999756 1.70052e-005 0
vn 1.00017 0.00492969 0

line 18423
vn 1.00014 -0.0104035 0
vn 0 0 0 vn 0 0 0 vn 1.00024 -3.12127e-006 0
vn 0.999756 0 0

It is mising the end of line character and so you have two or three vertices normals in the same line.

There are more wrong lines like this in the normals sections

The effect of this error will depend on what does the progran that reads this file.

1- If the programa doesn't use normal information in the obj file, the model will import without any problem just because all the normal information (right or wrong) is ignored.

2- If the program doesn't use normal information, but check the sintaxis can report that the obj file is wrong

3- If the program use normals, it will read the first normal in the line and ignore the second one or report an error of extra characters in the line. In any case it will be missing normals (less normals than vertices) and the read normals will all be wrong (a vertex has the normal of another vertex)

Stupidity also evolves!