Hello.
Thanks to you I found the problem!
Im using milimeters as my units. If I type the height of stairs as 2800mm it works fine but then once I enter set parameters it shows calculated rise as some weird number (see attachment). If that number is set then we get errors in Ruby console.
To fix the problem I need to change that strange number of Rise to regular number - say 180 - then change other parameters and then its possible to save.
Just need to adjust the height of stairs afterwards
Thank You!