Dear Paul,
Thank you for your response.
I am using the 20.1.11 version, and I tried the same code you provided with 3dNwarpApply function. However, this function does not take .1D files as input and the error I receive is that the "process was killed". Instead, I tried running 3dAllineate and 3dNwarpApply separately, with .1D files as the input for 3dAllineate and the _WARP.nii.gz file for the 3dNwarpApply. Applying both of them in series didn't lead to the same results as the @animal_warper function. Image warp.gif attached to this reply shows that.
I also tried applying the *_composite_linear_to_template.1D to my input and then applying the inverse of it (*_composite_linear_to_template_inv.1D) and supposedly it must get back to the input space, but it doesn't! Weird ... . Showed in image inv.gif.
Best,
Momo