Thanks a lot, purchase-interaction, for the file. So much more information.
The whole model was slightly titled. You can see that in the right or left view.
So I used the Parent to get it back to a leveled orientation (R.P. -0.3645º)
With that being done, I selected all but the Parent and used the Axis Tool, as shown in the image.
This left me with another problem, as the Parent had a tilted Axis but leveled polygons)
So I called up a new Null, selected all children of the previous group (Parent null not selected), dragged all under the new Null, copied and pasted the name to the new Null, and deleted the old Null.
There are other ideas to do that, but with this amount of elements, I prefer this method.
Screen Shot 2023-09-25 at 1.59.44 PM.jpg
All the best