The following example:

    \starttext

    abc\footnote[fn:abc]{footnote abc}\ abc

    def
    \startfootnote[fn:def]
      footnote def
    \stopfootnote
    \ def

    No problem here: abc\note[fn:abc]

    Problem appears here: def\note[fn:def]

    \stoptext

Generates a missing reference error for a reference provided on 
\startfootnote (and \startendnote) accessed by \note:

    references      > start missing references
    references      >    1  [][fn:def]
    references      > stop missing references

ConTeXt  ver: 2021.08.04 17:51 LMTX  fmt: 2021.8.4

There was no problem with previous versions.

-- 
Rik