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Here's section of THK's literature with a good reference of Bearing block models and bearing part numbers.

https://tech.thk.com/en/products/pdf/en_a15_299.pdf?#6

First off, is the undriven end of the ball screw constrained, from your photos I can not tell.

There does seem to be a large portion of the Z axis is unsupported, is there any flex/for & aft...