Came across this when trying to change a transmap which came with a purchased 3d item, in this case a hair model.

Transmap will display correctly, but when trying to alter it slightly in PS it appears that it was saved using  "pixel aspect correction ratio" and displays in PS as a long thin image, making it impossible to alter.

Is there any way to get over this please?

The greatest part of wisdom is learning to develop  the ineffable genius of extracting the "neither here nor there" out of any situation...."