It's not motorized and motorizing that type of stand is painful (there is at least one paper that shows it's possible; I tried it and the results were not great: https://journals.plos.org/plosone/article?id=10.1371/journal...)

What was the biggest challenge? I suppose you get some unpredictable backlash in that flexible shaft.

Yeah the flexible shafts were terrible. I'd get highly variable movement even when making movements in only one direction (IE, home to Y 0, then only move positive ). They were so bad I tried to find ways to mount the steppers directly on each axis, which means the Y stepper is hanging out in air putting a lot of weight directly on the Y stage.

Instead, i switched to cloning stages like this: https://www.asiimaging.com/products/stages/xy-inverted-stage... but I used off-the-shelf (well, amazon) linear rails, off-the-shelf (stepperonline) steppers, and 3d printed (or machined aluminum) frames. Works much better.