Filipe I think you are right when you say that my issue could be the play on the z axis. I didn’t understand what you were meaning at the first read of your post.
My middle definitely keeps out of square the x and y axes tending to make an angle lower than 90 degree. Pulling by hand the two axes I can easily keep them square, taking off the hands the middle flexes the two axes of a couple (more or less) of degree.
I think the cause of this problem could be the “better z middle” printed at 100% scale instead of the 98% scale that I used to print the other middle components. What do you think about this?
But, then again, Filipe, maybe the solution you mention for the play in the z axis could be right also for me, but I didn’t understand the exact point where you removed some pla and which bearing you put more inside. Don’t you have a picture explaining that?
Thank you very much!!!