Hi,

Another MWE that breaks tagging:

\setuptagging[state=start]
\starttext
\startchapter[title=Chapter]
\startitemize
\item Text
  \startitemize[columns]
  \item Text
  \stopitemize
\stopitemize
\stopchapter
\startchapter[title=Next Chapter]
  Text
\stopchapter
\stoptext

This time the structure tree is affected. The resulting tree (roughly) is
the following:

/document
  /section (chapter)
    /sectionnumber 1
    /sectiontitle Chapter
    /sectioncontent
    /itemgroup (itemize)
      /item
        /itemtag/math/mrow/mo •
      /itemcontent
        Text
        /itemgroup (itemize)
          /itemgroup (itemize)
            /item
              /itemtag/math/mrow/mo −
            /itemcontent Text
    /section (chapter)
      /sectionnumber 2
      /sectiontitle Next Chapter
      /sectioncontent Text

Note that the second chapter is located within the first chapter. I hope
that this can be fixed easily.

Thank you for any effort,
Christoph