This mwe gives the error below:
\starttext
{\spaceskip=1.0pt plus1pt minus1.5pt Matilda, 24, 345, 348, 361, 366}
\stoptext
Steffen
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… $ ~/context-osx-64/tex/texmf-osx-64/bin/mtxrun --script context --autogenerate /Users/steffen/Desktop/error_1.tex
resolvers | formats | executing runner 'run luametatex format': /Users/steffen/context-osx-64/tex/texmf-osx-64/bin/luametatex --jobname="error_1" --fmt=/Users/steffen/context-osx-64/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.fmt --lua=/Users/steffen/context-osx-64/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luametatex/cont-en.lui --c:autogenerate --c:currentrun=1 --c:fulljobname="/Users/steffen/Desktop/error_1.tex" --c:input="/Users/steffen/Desktop/error_1.tex" --c:kindofrun=1 --c:maxnofruns=9 --c:texmfbinpath="/Users/steffen/context-osx-64/tex/texmf-osx-64/bin"
fonts > beware: no fonts are loaded yet, using 'lm mono' in box
system >
system > ConTeXt ver: 2021.06.25 22:49 LMTX fmt: 2021.6.26 int: english/english
system >
system > 'cont-new.mkxl' loaded
open source > level 1, order 1, name '/Users/steffen/context-osx-64/tex/texmf-context/tex/context/base/mkxl/cont-new.mkxl'
system > beware: some patches loaded from cont-new.mkiv
close source > level 1, order 1, name '/Users/steffen/context-osx-64/tex/texmf-context/tex/context/base/mkxl/cont-new.mkxl'
system > files > jobname 'error_1', input '/Users/steffen/Desktop/error_1', result 'error_1'
fonts > latin modern fonts are not preloaded
languages > language 'en' is active
open source > level 1, order 2, name '/Users/steffen/Desktop/error_1.tex'
fonts > preloading latin modern fonts (second stage)
fonts > 'fallback modern-designsize rm 12pt' is loaded
tex error > tex error on line 4 in file /Users/steffen/Desktop/error_1.tex: Valid keyword expected, likely 'minus'