I tried your code. Indeed there is no blank page after the "Schmutztitel". So you need to add to the \startstandardmakeup[page=yes]. - Something
Moreover:
page=yes|right|... makes the same page break setting to both place: start...matter and stop...matter. I ussually need a different setting. For now I am solving it by
\setupsectionblock [frontpart] [page=right, after={\setvalue{\??sb\@@sectionblock\c!page}{}}]
the problem has to do with an overflow of makeup in grid mode (due to already present mark reset nodes); i uploaded a beta that (hopefully) corrects the problem (thanks to taco for analyzing that it was textheight related)
Hans
Good news the bug was fixed.
What I proposed was not related to mentioned error. It just recalled me this problem of coupled 'page' option and the need to be split.
Vit
Can you make a little example where a split 'page' option is from use? Wolfgang