..and finally making chips after a 3 year journey! Congratulations!

I would be grateful if you could measure the stiffness in the x and y directions.

What breakout board/ controller are you using? Does it have optocouplers on the inputs? I had the same problem feeding 24v signal to 5v bob. In my case the signal was fed to the optocoupler through a current limiting resistor with a value calculated for 5v input. I just had to replace the resistor with one calculated for 24v.