I guess you have got an inclined bed lathe.
With this type of machines the kinematic transformations (for example TRANSMIT) in reality is a concatenation of two transformation.
The first transformation converts the oblique machine coordinates into rectangular coordinates.
The second transformation converts the rectangular coordinates into the required format (for example into polar coordinates for TRANSMIT).
With TRAFOOF only the second transformation will be deactivated, the first transformation is "persistent". If this is true, you should see that the X1 axis is moving when you move the Y geometry axis (try with Jog in Y). So the X1 machine axis is still part of an active transformation and can not be moved with G75.
I'm sorry, but I don't remember if it is possible to deactivate the persistent transformation programmatically (i.e. without changing machine parameters).
And if it should be possible I don't remember how to do it.
But may be it helps to understand the problem.