Dear Pol stra, I run your sample and got the same error. After changing pre-stepwise to pre-60, I run it again, but the same error occurs.

!LuaTeX error: There should have been a lua <node> here, not an object with type string! ==> Fatal error occurred, no output PDF file produced!

I checked my file which include \StartSteps … \StopSteps and got the same error. It was working well before. Unfortunately, I don't know what is the problem. Experts will answer to it soon. My ConTeXt version is : This is LuaTeX, Version beta-0.70.2-2012052309 (TeX Live 2012) … ConTeXt ver: 2012.09.04 18:08 MKIV fmt: 2012.9.5 int: english/english Best regards, Dalyoung